Possible Clues:

• Ship's hdg
• San Diego-to-Las Vegas dir
• L.A.-to-Burbank direction
• Dallas-to-Des Moines dir.
• K.C.-to-Duluth dir.
• Birmingham-to-Huntsville dir.
• Bristol-to-Leeds dir.
• Pittsburgh-Buffalo dir.
• Palm Springs-to-Las Vegas dir.
• Miami-to-NYC direction