The union representing pilots for Tempe-based US Airways says the airline tried to intimidate a pilot into flying a malfunctioning plane last month. When she refused, the US Airways Pilots Association says, she was forced off the plane and "met by [the airline's] corporate security and escorted out of the airport."

In fact, the union claims, a total of six pilots refused to fly the plane before the airline agreed to make the necessary repairs.

This, according to the union, is just one incident representative of a "safety culture" based on "intimidation and disrespect" -- a culture the union exposed in a full-page ad in USA Today on Friday.

US Airways did not immediately return our call this afternoon. However, the airline has been in bitter contract negotiations with its union since 2005, and in an e-mail to employees Friday, Chief Operating Officer Robert Isom called the union's accusations a "smear campaign that in reality is all about contract negotiations, not safety." He adds that the plane in question "flew that day and performed flawlessly."

The pilots' union says, on June 16, Captain Valerie Wells, who has over 30 years of experience, thousands of hours of flight time, and a degree in aviation safety, was about to embark on a 3,000-mile, trans-Atlantic overnight flight from Philadelphia to Rome.

As the plane was pushing back from the gate, the union says, the auxiliary power unit, a backup source of electrical power, and the Hot Battery Bus, a critical source of primary electrical power, failed. This left the plane with no electrical power and no radio communication.

The union says Wells was forced to open a window to yell down to the ground crew to alert them to the malfunction.

According to the union, "US Airways maintenance was able to restart the power unit, but offered no explanation as to why it failed or any reasonable assurance that it wouldn't fail again."

Wells, not wanting the plane to lose power in the middle of the night as she and the 300-plus on board were thousands of feet above the Atlantic Ocean, the union says, refused to fly the aircraft and forced a maintenance crew to address the malfunction.

Meanwhile, the passengers were growing antsy. The fact that the air-conditioning needed to be turned off as mechanics worked on the plane certainly didn't help things.

Wells, the union says, was forced to "make sure the temperature wasn't unsafe -- for passengers of any age or health condition -- and balance those concerns against the goals of Customer Service agents who are frequently resistant to deplaning the passengers because of the pressure to be on time."

US Airways officials then "embarked on a plan to intimidate the Captain and her crew to try to get them to fly the airplane without fixing it. Not only did mechanics try to convince her to disregard the problem, but her supervisor called her repeatedly and put tremendous pressure on her, specifically asking if she was 'refusing to fly.' At US Airways, pilots who refuse direct orders are putting their jobs at risk," the union says.

Another flight crew was called in to fly the plane and experienced the same problems as Wells -- not once but twice. It was only then that the plane finally was removed from service and repaired.

The flight finally left Philadelphia 11 hours late, with a third flight crew.

Check back for updates.