Federal air-safety watchdogs on Friday recommended changes to ensure that emergency cockpit-oxygen systems on thousands of Boeing airliners are properly designed to help pilots fight windshield fires.

The National Transportation Safety Board urged action to lengthen hoses for such oxygen systems, including those installed on certain Boeing 757 and 767 models, so pilots can keep their masks on while retrieving fire-extinguishers stored at the rear of the cockpit.

Concerned...