Flights attendants at American Airlines are to stage protests at 11 airports across the United States on November 15 as a dispute over protracted contract negotiations begins to escalate.

The Association of Professional Flight Attendants (APFA) which represents around 28,000 crew members at the Dallas Fort Worth-based airline says management has largely rejected its latest set of proposals which included “reasonable improvements” for its members.

The negotiations cover nearly every aspect of the collective bargaining agreement held between American Airlines and its flight attendants, and while progress has been made in many areas, the two sides remain at odds on a growing list of agenda items.

And there are even more proposals that are yet to be discussed that could cause even more friction, including a demand from the union to pay flight attendants for boarding and improve sick leave provisions as well as the number of vacation days flight attendants get to enjoy.

“American is resisting much-needed contractual improvements for our workgroup, which address operational reliability challenges and improve work-life for Flight Attendants,” the union said on Wednesday as it announced plans to carry out information picketing events at some of AA’s largest hubs.

So far, events are scheduled to take place in Boston, Charlotte, Chicago, Dallas Fort Worth, Los Angeles, Miami, New York JFK, Philadephia, Phoenix, San Francisco, and Washington DC.

The union is expected to use the events to complain that catering issues at the airline are resulting in a “substandard” service for passengers and will argue that continuing staff shortages mean passengers suffer when bad weather or other delays lead to irregular operations.

APFA says that while American Airlines is working to bolster its workforce, attrition is also on the rise because flight attendants are suffering from “exhaustion and decreased morale.”

Informational picketing by airline staff in full view of passengers is relatively common, and airports witnessed both Southwest Airlines and United Airlines flight attendants carry out similar protest action in September over their own contract disputes.

The dispute has got so bad at Southwest Airlines that the flight attendant union has agreed to enter into mediation with the airline in an attempt to find a way forward.