A 2mg startng dose of Xanax to just kill anxiety on a plane ride?
That seems a bit high to me personally and is more for the order of a recreational Xanax dose, which doesn't seem to be her purpose. While the answer technically is correct, here is a perhaps a more practical real-world answer in regards to benzo's and flying.
Consider everything that your flight will entail along with your tolerance and familiarity with benzodiazapines.
2mg Xanax could possibly knock you out for the flight which could have serious ramifications. Being unconcious while flying is not a good idea, lots of problems can occur such as it causing you to miss a connecting flight, or be asleep when your plane is hijacked by muslims...
Also...
Are you going to be having complientary drinks on the flight? Alcohol is delightfully synergestic with benzo's and also potentiates the effects. And again, since passing out is the problem, and 2mg Xanax with a few drinks is a pretty guaranteed way to fall into a deep blissful sleep.
Personally depending on the duration of the flight, the level of lucidity needed, the amount of anxiety reduction required and other factors, it would be wise to start with a small to moderate dose, since the anxiety reduction effects of the benzo come with even very small doses...
Proposed Soultion:
Ingest .5 mg roughly an hour or two before the flight perhaps with a drink or so. If anxiety persists add another .5mg and work in those increments. Guage your levels of lucidity and relaxation and feel your way into the plane ride rather than chance it all on a possible knock out dose and fuck up your trip...
Brainrape
PS- Perhaps a better analogy is to take the benzo's much the same way a person takes them prior to an acid trip, a low dose whose primary purpose is to reduce anxiety and nothing more, in which case most often.5mg Xanax is the suggested doseage...