Deep Sea, Ocean, store brand are all fine, and some come in travel size. They usually contain a preservative.
As mentioned one can't treat viral infections. But to prevent bacterial infections I've heard travelers putting a bit of triple antibiotic ointment in the nostrils. I usually wipe down tray tables and armrests. Seat back pockets and in-flight magazines harbor bacteria too, though many people don't think about those. Hydration is important. Happy travels.