The private aviation glossary
104 terms explained in plain English — from ACMI to wet lease.
A
AD / SB (airworthiness directive / service bulletin) operations
An airworthiness directive is a legally binding order from a regulator such as the FAA or EASA requiring an inspection, modification or repair to correct an unsafe condition on a particular aircraft or engine type, with a deadline. A service bulletin is a manufacturer's recommendation for an improvement or fix, which is optional unless a regulator adopts it as an AD or an operator's programme mandates it. For buyers, the status of ADs and major SBs is a core part of the records review: an aircraft with outstanding ADs cannot legally fly, and one behind on important SBs may need expensive catch-up work before it can go on a charter certificate.
APIS operations
Advance Passenger Information System is the electronic transmission of passenger and crew passport details to a country's border authority before an international flight departs. The United States requires it for all private flights arriving in or leaving the country, generally at least 60 minutes before departure, and the operator must receive a clearance message before take-off; the EU, UK, Mexico, India, Brazil, China and many others run equivalents. This is the practical reason charter operators need everyone's passport details a day or more in advance and why adding a passenger at the airport is often impossible on an international flight. Data goes through the operator or its trip-support provider.
B
Block time operations
Block time is the elapsed time from the moment the aircraft first moves under its own power, when the chocks or blocks are pulled, to the moment it comes to a stop at its destination. It includes taxiing and any waiting on the ground with engines running, so it is longer than airborne flight time by 10–25 minutes on a typical sector and much more at congested airports like Teterboro or Heathrow. Most charter operators bill by block time, so a quote based on flight time can understate the real cost; ask which the operator uses and, if it is block, whether there is a cap for taxi delays beyond your control.
C
Ceiling (weather) operations
In weather reporting, the ceiling is the height of the lowest layer of cloud covering more than half the sky, measured above the ground. Along with visibility it determines whether an airport is usable: every instrument approach has a minimum ceiling and visibility, and if the reported weather is below them the crew cannot legally attempt to land. Small airports with only basic approaches may need a ceiling of 800–1,500 ft, while a major airport with ILS Category III can accept a few hundred feet or less. When a charter operator warns that low cloud may force a diversion to a larger airport, it is the ceiling they are watching.
Crew duty limits operations
Crew duty limits are the regulatory caps on how long pilots may be on duty and how much rest they need between duties. Under FAA Part 135 a two-pilot crew is generally limited to 14 hours of duty and 10 hours of flight time, with at least 10 hours' rest; EASA rules are broadly similar but vary with start time and number of sectors. The clock starts when the crew report, not when you board, so a late departure or a long lunch stop can push a crew out of limits and require a second crew or an overnight. This is why operators ask for realistic timings and why a 4 a.m. departure after a late-night arrival is often impossible without a crew change.
D
De-icing operations
De-icing is spraying heated glycol-based fluid on the wings and tail to remove snow, frost or ice before take-off, sometimes followed by a thicker anti-icing fluid that keeps new precipitation from sticking for a limited holdover time. Aircraft cannot legally take off with contaminated wings, so on a winter morning in Chicago, Moscow, Zurich or Aspen it is not optional. It is usually not included in charter quotes because it is unpredictable: a light jet costs $500–$2,000 to de-ice, a large-cabin jet $3,000–$10,000, and in a snowstorm queues of an hour or more are normal. Hangaring the aircraft overnight is often cheaper than de-icing it in the morning.
E
ETOPS operations
ETOPS, Extended-range Twin-engine Operational Performance Standards, governs how far a twin-engine aircraft may fly from the nearest suitable airport, expressed in minutes of single-engine flying time. It was written for airlines, and many business jet operations are exempt or use similar oceanic rules, but it becomes relevant for bizliners and for Part 135 operators flying twin-engine jets over long stretches of ocean, where the aircraft, maintenance programme and crew must be specifically approved. For a customer this occasionally explains why a particular aircraft cannot take a direct routing across the South Pacific or must add a technical stop on a remote route while another type of the same size can fly straight.
F
FANS (Future Air Navigation System) operations
FANS is a set of datalink technologies, principally controller-pilot datalink communications and automatic dependent surveillance, that let aircraft exchange text messages and position reports with air traffic control by satellite instead of voice on HF radio. FANS 1/A equipment is required to fly in the most efficient North Atlantic tracks and increasingly in Pacific and Asian oceanic airspace. Aircraft without it are routed onto less direct tracks or lower altitudes, which can add 20–40 minutes and fuel to a transatlantic flight. Most business jets built after about 2012 have it; older aircraft may have been retrofitted, at a cost that buyers should factor in.
Flight time operations
Flight time, or airborne time, runs from wheels-up to touchdown and is the figure most people have in mind when they estimate a trip. A Phenom 300 from Miami to New York flies for about two hours forty minutes; the block time will be closer to three hours. Charter quotes may be built on either measure, and some operators use flight time plus a fixed taxi allowance of 6 or 12 minutes per sector. For jet card and fractional contracts the definition matters even more because hours are the currency: 'block plus 12 minutes' contracts consume noticeably more hours a year than 'flight time' contracts for the same trips.
G
General declaration operations
The general declaration, or gen dec, is the standard ICAO customs document that lists an international flight's aircraft, crew, passengers, route and any declarations, and is presented to customs and immigration on arrival and sometimes departure. The crew or handling agent prepares it from the passenger details you provide; that is why operators ask for full names, dates of birth, nationalities and passport numbers well before the flight. Errors on the gen dec, such as a mis-spelt name or expired passport, can delay clearance or lead to refusal of entry, so send exactly what is printed in the passport rather than a nickname or a shortened name.
M
MEL (minimum equipment list) operations
A minimum equipment list is an approved document that specifies which items of equipment may be inoperative for a limited period while the aircraft continues to fly safely, and what conditions or limitations apply. If the second coffee maker or one of two cabin entertainment screens fails, the MEL lets the flight go ahead with the item deferred; if an anti-ice system or a transponder fails, it generally does not. For a passenger, an MEL deferral is a normal, regulated part of operations rather than a sign of neglect, although the crew should tell you if it affects the cabin. A pattern of many open MEL items on one aircraft is a different matter.
N
NBAA IFR reserves operations
NBAA IFR reserves are the fuel allowance that business jet manufacturers assume when publishing range figures: enough to fly to an alternate airport 200 nautical miles away (100 nm for smaller aircraft), hold for 30 minutes and land with a margin, on top of the fuel for the trip itself. Because the assumption is standardised, brochure ranges from different manufacturers are comparable, but they still represent a best case with a light passenger load, no headwind and ideal routing. In practice an operator's flight planning will often demand more reserve for weather or remote alternates, which is why the achievable range on a real day can be 10–15% less than the number in the brochure.
O
Overnight (RON) operations
RON stands for 'remain overnight', the operational term for an aircraft and crew staying at a destination between your outbound and return flights. Overnights add crew hotels and per-diem, aircraft parking or hangarage, sometimes de-icing in the morning, and the daily minimum on days the aircraft does not fly. For a two-night trip on a light jet these extras typically add $2,000–$5,000; for a large-cabin jet with three crew at an expensive destination, considerably more. The alternative is a 'drop and return' where the aircraft goes home and comes back, which costs extra flying but avoids waiting charges; the break-even is usually around two to three nights.
R
RVSM operations
Reduced Vertical Separation Minimum allows aircraft between 29,000 and 41,000 ft to be separated vertically by 1,000 ft instead of 2,000 ft, doubling the usable flight levels. It is standard in nearly all the world's airspace, and an aircraft must have certified altimetry and autopilot equipment plus an operator approval to fly in it. An aircraft without RVSM approval is restricted to below 29,000 ft, where fuel burn is much higher and weather worse, which cripples a jet's range and comfort. When buying an older jet, confirm the RVSM approval is valid; when chartering, it is a given on any properly operated aircraft.
T
Tail number operations
The tail number is an aircraft's registration painted on the fuselage or tail, for example N123AB or G-JETX, and it is the single most useful identifier a charter customer can ask for. With it you can look up the owner, the age and model of the aircraft, whether it is on an operator's Part 135 or AOC list, its recent flights on tracking sites and any accident or incident history. A quote that will not commit to a tail number until the day of departure is not necessarily suspicious, since floating fleets swap aircraft, but the operator should be able to name the specific aircraft, or at least the type and operator, before you pay.
Trip support operations
Trip support is the service of planning and coordinating everything an international flight needs beyond the flying itself: overflight and landing permits, slots and PPR, handling at each airport, fuel arrangements and credit, customs and APIS filings, crew visas and hotels, weather and NOTAM briefings and 24-hour operations support. Companies such as Universal Weather and Aviation, World Fuel, Jetex, UAS and ExecuJet provide it to operators and flight departments, and their fees appear inside international charter quotes. For an owner running an aircraft with a small crew, a trip-support contract is what makes a trip to Lagos or Ulaanbaatar routine rather than a research project.
W
Wheels-up time operations
Wheels-up time is the moment the aircraft leaves the runway, as distinct from the departure or block time when it starts to taxi. Operators and air traffic control plan around it: a slot at a coordinated airport, an oceanic clearance, or an arrival before a curfew is usually expressed as a required wheels-up time, and the crew will ask you to be at the FBO 15–30 minutes earlier so that boarding, doors closed and taxi can happen in sequence. On a jet card contract the phrase is often used loosely to mean the departure time you book; on an operations sheet it is precise, and being ten minutes late can cost the slot.