The main problem that contributes to your cold catching is the extremely dry air in pressurized aircraft. This dries out the sinuses and makes one more susceptible to infection by viruses. The key is keeping the sinuses hydrated. As a pilot for many years and with this being a common affliction among those of us who spend hours in the dry environment, I'm never very far away from a small, inexpensive bottle of saline solution that is sprayed into both nostrils at least once per hour. In the c0ckpit, there's a lot of up-sniffing to get the moisture into all the sinus cavities. You can do the same thing in the lavatory. A brand name I use is Ocean's, but I'm sure there are several over the counter solutions. It's not the typical nasal spray in that it has no medication that can cause rebound effect. Give it a try next time... can't hurt! Best of luck!