This could be a game pack and named as The Sims 4 : Fly High, or something to be introduced in a world adventure-ish expansion pack.
An airport lot could be included in the pack, and new career choices such as the flight attendant and the pilot career could be introduced (may be active careers).
The interior of an airplane could be some types of special lots, which will be activated only if a sim bought air ticket and aboard a plane. The might be several hours for the sims to spend in the plane and served with foods. They may chat with the other passengers, woohoo in the toilet, or even prank in the captain's room. The handphones are inaccessible in a flight, as the sims will not be able to call anyone.
A new item included would be luggages, which Sims may be able to bring some personal stuff and souvenirs in it. The luggages randomly lost in the game and the sims would be get an insurance payment only if they buy it earlier in the airport.
The new themes introduced as new worlds (that would be inaccessible except travel by plane) might be an Egyptian, a Tropical as well as an Oriental one.
Also, rich sims would be able to own private jets in their home. They may need a license to be able to drive them. A new death type would be plane crash.