If you have a stellar resume outside of your busts then you still have a shot. If it was a long time ago and you have since progressed in your career (passed a type ride, been hired and passed training at a part 121 or charter dept) you should be ok. If you are a flight instructor with three busts it will definitely hold you back. As far as I know they are not hiring people with three busts unless they are exceptional candidates in every other way.