“The safety and well-being of our passengers is the highest priority for United pilots, and this should not have escalated into a violent encounter,” says a letter from United Master Executive Council, the union representing United’s 12,500 pilots, Business Insider reports. “United pilots are infuriated by this event.”

The letter also seeks to direct some of the blame away from United (UAL). “This occurred on one of our contracted Express carriers, separately owned and operated by Republic Airline, and was ultimately caused by the grossly inappropriate response by the Chicago Department of Aviation,” it says. “No United employees were involved in the physical altercation.”

“We cannot let this huge distraction affect our ability to do our jobs,” the letter continues. “We have successfully flown through more turbulent times, and we will weather this storm as well.”

United Airlines CEO Oscar Munoz has apologized for the incident. “No one should ever be mistreated this way,” he said in a statement Tuesday. “We take full responsibility and we will work to make it right.”