I haven't seen any in the property list. Is it possible they're unlocked at a higher level?
The Rockstar Social Club website has added a handy online guide. It has an entry for the website where you can purchase aircraft from with the following text:
- Vehicles bought from Elitas Travel can be delivered on request by calling Pegasus – the contact will appear on your phone when you purchase your first vehicle requiring their services.
- Vehicles delivered by Pegasus will be blipped on the Map, you can then use Quick GPS to navigate directly to your awaiting vehicle – look for ‘Pegasus Vehicle’ in the Quick GPS list.
The description for the website that sells boats is exactly the same.
This leads me to believe that you call it in, and the plane will be delivered to the closest airfield. Kind of like how the blimp works in Story Mode.