Pilot bars could refer to the epaulette stripes that denote whether you are captain (four bars) or first officer (three bars). It could also refer to establishments that serve alcohol and which are frequented by pilots. There's one or two within a short cab ride of all but the most desolate airport. Before you go into the latter kind of bars, you have to remove the former kind of bars, along with your tie, your wings, and any other company identification, because most companies have a policy forbidding pilots drinking alcohol while in uniform, or while displaying company insignia.
The typical pilot shirt has a company logo embroidered over the right pocket, so technically you can't go to the bar after work without having a t-shirt or something to replace the shirt. In reality, we ditch the tie and the bars and wear the same sweat-soaked shirts to drink our beer as we did to land the airplane. A friend of mine, observing the lame tactics, such as turning down our lapels or scrunching into the corner, that we employ while trying to hide our logos suggested that pilot bars should have a supply of big happy-face stickers at the door, for us to paste over our company logos.