I would say that the trays are not easy to transport as the 34;lid34; is loose fitting and its lip merely rests on the tray via gravity. While the lip of the lid prevents the cover from easily sliding off, it does not 34;snap34; or lock into place and thus will likely 34;pop off34; if the tray is tilted or jostled too much. Additionally, since the cover merely rests on top of the tray, it offers no way to seal the tray to make it 34;air proof34; as you say. It would seem that the lid is there merely to keep items warm and/or temporarily protect food. Admittedly, we do not use the lids much at all. When storing the trays we nest all three of them together and put all three lids underneath the stack. Also, the metal is on the thinner side and is susceptible to small dents or dings through use. All told, the kids love them as they can keep their food 34;separate34; and we like them because it helps with portion control!
Rating: [4 of 5 Stars!]