Consider everything that the director, John McTiernan, and his screenwriters, Jeb Stuart and Steven E de Souza, set up in this brief little scene. Though Bruce Willis plays McClane as the modern American cowboy, Roy Rogers with an attitude, the film-makers choose to emphasize his vulnerability first. His fear of flying gets us primed for the bumps and bruises he will sustain all night long, when a phalanx of terrorists take over a Christmas party at Nakatomi Plaza.
I know because I watched them all a couple of weeks ago.
Everything in that quote is Die Hard, not Die Hard 2. Die Hard took place at Nakatomi Plaza on Christmas Eve. McClane's fear of flying is noted at the very beginning of the film. Die Hard 2 was the airport in DC, where McClane took on Colonel Stuart and his cronies.