As a commercial pilot for many years, I find that the malady is frequently experienced by those of us who fly nearly every day. One thing that seems to help and is quite simple is the use of saline spray regularly. It can be purchased in squeeze bottle applicators, has no medication that can cause "rebound effect" and costs less than two dollars U.S. It irrigates the sinus passages and keeps the mucous membranes in a naturally "wet" condition which helps them to produce the mucous necessary for healthy sinuses. The problem that occurs with sinusitis is a small area within the sinus cavities is isolated by swelling mucuous membranes, and ceases to be exposed to oxygen. Oxygen controls the bacteria that inhabits the sinuses. Once the O2 is cut off the bacteria "blooms" and causes the infection to spread. This is one of the reasons a sore throat is always a precursor to sinusitis... the infected mucous drains down the back of the throat causing the pain and redness.
The saline should be used at least once in each nostril every 2 hours... more often is even better. This should be done in private since to be really effective a lot heavy "up-sniffing" is required to get the saline in the areas in the forehead and isn't very pleasant for those witnessing.
At any rate... works for me and many that I know for whom the infection is a work hazard. (The constantly changing pressure irritates the sinuses, cusing them to become inflamed, according to our company Doctor).