Altitude isn't the only factor. Vibration is a big problem for some wines (they become metallic tasting); this is highly individual by the wine. Great wines require 3 to 6 months rest after being transported to recover; almost everyone would be able to taste the difference.
There are many wines that can cope with the harsh environment on air planes. Some even taste better than on the ground. Delta used to have an excellent F wine list; now it is plonk (it also costs them 10% of what they used to spend). A good example of an airline where every wine is excellent is Cathay Pacific in F. But I checked the prices on their current list, and every single wine served by CX in F sells for over USD 100 per bottle with the most expensive selling for almost USD 200! At the end of the flight they have to pour the partial bottles out; I was the only F passenger on my last flight, drank 4 different wines (champagne, 1 white, 2 red) and that was over USD 500 in wine down the drain. This is why UA doesn't spend more than USD 10 per bottle on their wines. Despite the lavish wine spending, CX had record profits last year (or perhaps because of the lavish wine spending). That was before SARS decimated their business.