WASHINGTON (Bloomberg) — UAL Corporation's United Airlines, the second-largest US carrier, and BMI, third biggest in the UK, may start coordinating flight schedules March 30 without violating antitrust laws, US regulators said.

The carriers won antitrust immunity in 2002 and were barred from implementing it until the US and European Union reached a so-called Open Skies treaty. With that agreement reached and set to take effect March 30.