I'd suggest using decongestant tablets, ask for a water from the crew, hot preferably but cold is also okay (but you don't need a lot so you'll have to drink some first) and dissolve some crystals into the water and sniff them whilst descending (20 mins before landing), otherwise olbas oil needs no dissolving because you an just put it on fabric or tissue etc to sniff, but it isn't as hardcore as menthol crystals. I'd also recommend, ear plugs made for assisting with air pressure.