In a letter sent to American employees by Kimball Stone, American’s vice president of flight, the company said changes to its network will “improve aircraft utilization and simplify hub operations, continue to earn the loyalty of our customers and enhance career opportunities for our team members.”

“While this decision has been in discussion for a while, it’s obviously not the news our STL pilots want to hear,” Stone’s letter continued. “But I believe it is important to share this as soon as possible so everyone affected by this announcement, including our STL Flight Office staff, can begin talking about options and the decisions ahead. A sufficient number of positions exist in other crew bases and, of course, transfers will take place according to the joint collective bargaining agreement.”

Companywide, American has 800 employees in St. Louis, including pilots.

The Allied Pilots Association, the pilots union, sent an email to pilots Monday stating that the union’s St. Louis representatives, its negotiating committee and contract compliance committee “will closely monitor all STL base closure-related activity to ensure full compliance” with the APA’s collective bargaining agreement with American. The APA declined to comment on the pilot base closure beyond the emailed statement.