WASHINGTON » The union representing nearly 45,000 airport screeners has reached a first-ever collective bargaining agreement with the Transportation Security Administration.

The agreement Thursday comes more than a year after TSA head John Pistole agreed to grant screeners limited union rights for the first time since the agency was formed in 2001.

It includes a new process for resolving disciplinary matters and a better system for increasing pay based on performance, said John Gage, president of the American Federation of Government Employees, which represents TSA workers.

"What this contract will do is provide for increased uniformity on fair treatment and the other issues important to employees across the nation’s airports," Gage added.

The agreement was reached after months of tough negotiations and with the help of federal mediators.

Union members still must vote to ratify the contract.

Screeners who X-ray bags and guide passengers through security had been among the few federal employees without union rights. The decision to allow TSA workers to unionize prohibits them from negotiating over security matters. They are also banned from going on strike or conducting work slowdowns.

One of the biggest changes under the new deal is that disputes about serious disciplinary matters will be decided by independent third-party arbitrators at the federal Merit Systems Protection Board rather than TSA managers.

"We improved in all areas," Gage said.