From: Dear AFA
Interline travel agreements give us opportunities to purchase leisure standby travel tickets with other airlines. United has introduced Zonal Employee Discount (ZED) e-Ticketing for interline travel with 20 more airlines through a partnership with ID90T. United recently finalized their testing and went live with the ZED program, with the approval of these carriers:
Upon this launch, some carriers realized they required a certain code in the ticketing field that United did not use. The company is working now to enhance United's system to include this code to assist with new launches in the future. More information on interline travel can be found on United's Working Together website.