I suggest you have a hearty breakfast if you are going to fly in the morning and see if it helps. If it does, then its just bad nutrition. While I was training I used to get motion sickness because my flights where at around 5AM and didn't have time to do anything. After I started eating like I was supposed to and drinking lots of water, it went away. Don't know if its related to your problem but just give it a try. If you are worried about getting fat then just walk an extra 10 minute or something. Breakfast is the most important meal. Flying is stressful and you loose allot of energy doing it.