Halachah requires ritual hand-washing before eating bread. However, getting up to wash your hands before a meal on a flight can be a hassle and disturb other passengers. Cue the expanded use of the hybrid known as mezonot bread. This is bread that is made with juice and therefore is like cake. It does not require washing because its blessing is mezonot not hamotzi, the standard blessing on bread.
With mezonot bread, it would seem that passengers could have a roll with their meal without getting up to wash. Not so fast. Part of the halachic definition of cake is something that you eat as a snack and that you would not normally have alongside savoury food. While mezonot bread might be made with a sweet liquid, it’s usually eaten as part of a meal and with savoury food. For this reason some people take a sceptical view of mezonot bread and wash their hands for a meal where it is served.