This particular incident happened in the middle of the night at the North Las Vegas airport. My first flight of the night repositioned the airplane there from my home airport in Southern California; then, having picked up about 1200 lbs of cancelled checks in Las Vegas, I was to fly them to Burbank. While doing the before start checklist, however, I discovered that the #1 emergency boost pump was inoperative. I checked circuit breakers and cycled the switch several times, but nothing happened. I reluctantly pulled out my cell phone and called the chief pilot. It was 3AM.
"Ummm....ahhh....hellooo?" mumbled my boss when he answered on the fourth ring. Once he woke up enough to remember who Sam was, he was obviously unhappy about me calling at 3AM.
"Hi Ari, I'm sorry to call at this hour," I began, "but the #1 fuel boost pump is inop. I'm in Vegas."
There was a pause at the other end of the line, and then: "Umm, do you need it for starting? You could use the crossfeed valve and the other fuel pump."
I didn't like where he was going with this. "Well, Ari, it's required for flight."
Again, a pause. "Hmmph. Well...there's no maintenance this late...Would you be comfortable flying one leg to get the plane back home?"
I really didn't like that question. First, it would be illegal. More importantly, I was about to take a Weedwhacker near max gross weight over the mountains and desert in the middle of the night. I was most assuredly not going without a backup fuel pump. I chose my words carefully. "I'd really rather not, Ari. The airplane is unairworthy."
"Fine," Ari grunted. "I'll be there in a few hours." Click.
I had a few hours to reflect on how PO'd my boss would be when he got here. The eastern sky was beginning to get light when another Weedwhacker landed and shut down next to mine. My boss clambered out and wordlessly began throwing bags out of my plane. Finally he spoke: "Take that airplane to Burbank. I'll fly your airplane home." He brusquely climbed onboard the broken aircraft, started up, and taxied out for takeoff, leaving me alone to load the new airplane and reflect on what the consequences would be for me. As it turns out, there were none. I never heard of the incident again.
There are three sources of pressure for professional pilots. Company pressure, like I experienced, is only one. It is most widespread in the lower echelons of aviation, particularly in the FAR 135 freight world. What I experienced was actually a pretty benign example of "pilot pushing." Other pilots have been fired for refusing unairworthy airplanes or flights into hazardous weather.
A second source is social pressure from fellow pilots. While nobody wants a reputation as the company daredevil, neither do you want to be known as the pilot who scraps flights at the drop of a pin. You run into situations where doing the right thing is sure to cause more work for your fellow pilots. Sometimes they will be pressured to take the same unairworthy airplane that you refused. You feel bad about putting them in that position.
Perhaps the most common source of pressure is not external, but internal. Pilots tend to be very goal-oriented people. We want to find a way to complete the mission. Additionally, saying "no" is bound to cause a lot of inconvenience and perhaps even conflict; it's just a lot easier to say "yes" and go with the flow even when it's not the right thing to do.
According to the FAA, it is always illegal to fly an airplane with anything broken until it gets fixed or deferred in accordance with an approved Minimum Equipment List. The reality is that if it doesn't affect safety of flight, most pilots will conveniently "discover" the inop equipment on the leg that they're inbound to a maintenance base. So there are a lot of grey areas, and knowing when to put your foot down takes good judgment born of experience.
When you've made a decision, you need to stick with it. Don't let yourself be talked into doing something you don't want to do. If you've made an exception once, you'll make it again and again, and you'll find it harder and harder to say "no" when you're asked to do something that's truly a bad idea.
I know that a lot of people who read this blog are in the process of becoming professional pilots. Someday, you will find yourself in a very uncomfortable situation where doing the right thing may cause a lot of inconvenience to yourself and others, may bring the scorn of coworkers and the wrath of your boss, may even cause you to lose your job. Standing firm will carry a price. It is important that you accept that right now as the price of being a professional pilot.