Here are some project ideas for
Market trends for traffic, aircraft types, delays, etc.
Compare historical performance of various airlines
Flight traffic between airports shown on a map
Animation of flights shown on a map
Delay prediction ( there are many notebooks available online but they use outdated data)
I have described public data sources are available for domestic US airline travel. Data for international travel is not easily available. Please drop me a note if you are aware of any public data for any other travel markets.