I just flew with my almost 5 month old. While she slept in her carseat during takeoff and landing, she was up and wanted to be out during the middle of the flight. I got a toy that suctioned onto the tray and it was the best $8.00 I ever spent. As a plus, it suctions on restaurant tables and her bumbo tray as well.
The other toy that kept her entertained was a snack bag of chips. She loves the noise they make and tries, unsuccessfully, to get them opened.
Re: Tip for flying with baby:
this is the one i got:
https://www.toysrus.com/product/index.jsp?productId=3502330&CAWELAID=327246017