Most airlines do not typically have restrictions directly associated with food carried on to the airline during air travel. It is common for people to bring snacks or other processed foods with them as a cost effective alternative to purchasing food from the airline. With TSA rules, however, the foods that can be expediently carried are restricted to non-liquid and non-gel like products. This means that common snack foods such as yogurt and gelatin should not be packed with other items carried on board an airline. Otherwise, you can carry on whatever food you like including dishes you have prepared yourself. International air travel, though, can bring additional restrictions either in regard to limits, taxes, or other fees so it is best to look into customs policies of nations you may be visiting. Many countries do not allow importation of any fruits or vegetables, so those would need to be consumed before landing if even allowed on the plane to begin. The air travel business focuses on customer satisfaction which makes the use of airline enforced food policies uncommon. With such expensive rates of air travel, it is becoming common to avoid extra costs associated with airline offerings.
I have to say that when traveling with children or on long flights it is a great idea and advisable to bring healthy snacks on board if not restricted, considering what is offered on many airlines is less than desirable for your health and nourishment.
Share some of your ingenious ideas for healthy snacks to bring when engaging in airline travel in comments section.