Well, time flies when you're having fun, eh?
Five years ago today, I released the first version of what is, I'd like to think, the definitive aircraft set for (Open)TTD(Patch).
Today, the GRF has more than doubled in size from the original release, up to a massive 62 vehicles (plus 12 generational upgrades) for OpenTTD. Features such as variable speeds and running costs make this set as interesting as aircraft can be within the current spec, and I will continue to update it into the future as new features like newgrfairports continue to make the air game more challenging and enjoyable.
2.0 Changelist:
Additions:Bug Fixes:
- Added Short S.26 Empire flying boat (OTTD with "seaplane preview" parameter set only).
- Added Handley Page Type W as optional replacement for the Fokker F.VII.
- Added Junkers JU 52 as optional replacement for the Lockheed Electra.
- Added Bristol Freighter as optional replacement for the Lockheed Constellation.
- Added de Havilland Comet as optional replacement for the Sud SE-210 Caravelle.
- Added Noorduyn Norseman, Antonov An-2, Yakovlev Yak-40, Ilyushin Il-76, Beech 1900, Pilatus PC-12, Orville Sub-Orbiter and Sikorsky S-64 Skycrane (OpenTTD only).
Statistic Changes:
- ATR-72 no longer expires (again).
- Fixed running costs for Embraer ERJ 145.
Feature Changes:
- Delayed introduction dates of the Boeing 2100 and J-Tech J-1 Roku by 10 years.
- Slightly decreased purchase costs for Farman F.60 Goliath, Fokker F.VII, Handley Page H.P.42, Lockheed Electra and de Havilland Dragon Rapide.
- Reduced passenger capacity of the Fokker F100 to 97.
- Reduced goods capacity of the Farman Goliath and Fokker F.VII to 10.
- Reduced freight capacity of the Boeing 747 to .5x the goods capacity, to match other aircraft.
- New generation for Boeing 747 (747-8 from 2012).
- Generational stats for the Lockheed Constellation (Super Constellation from 1952, Starliner from 1957).
- Added 15 years to the model lifespan of the Lockheed Constellation.
- Added 5 years to the model lifespan of the Handley Page H.P.42 and Farman Goliath.
- Speeds of Westland Whirlwind, Sikorsky S-61, and Boeing-Vertol 234 reduced from Vno to realistic cruise speed.
- Purchase and running costs of above helicopters altered slightly to compensate.
- Boeing-Vertol 234 no longer expires.
- Decreased purchase and running costs, and capacity, for the Lockheed L-100 Hercules.
- Re-rendered slightly smaller sprites for the Lockheed L-100.
- Lockheed L-100 can no longer carry passengers.
- Added increased cargo decay times for luxury, small, and early aircraft (OpenTTD nightly builds only).
- Special refits (Combi, Airliner, Oversize, Sling, No tip tanks, and Float) can now be any of the four colour refits too.
- Added a newgrf warning message if planespeed is not 1/1.

Bug reports, suggestions and feedback to the development thread, please. More information about the GRF and the aircraft in it is available from the wiki page.
Download from Bananas, the OpenTTD in-game content.