Today Delta Connection carrier ASA applied with DOT to replace Delta's one daily Los Angeles-Guadalajara 738 flight with two daily ASA CRJ-700 flights around March 2006.
Although the US-Mexico air treaty was recently liberalized to allow up to three US and three Mexican airlines per US-Mexico route, this rule only applies to select resort destinations. Guadalajara is still a 2-carrier route. ASA's application approval, however, is not assured, even though this might just seem like a "simple" switch from mainline to connection. Since Delta and ASA are still seperate airlines, Delta must give-up their LAX-GDL route authority, they can't just transfer it to ASA. Therefore, any other US airline is able to apply for this route, which is the fourth busiest US-Mexico city pair, after Miami-Mexico City, New York City-Mexico City, and Los Angeles-Mexico City.