As Southwest goes, so go the legacy airlines. At least in the case of Southwest’s latest airfare sale for 14-day airfare, US Airways quickly matched the airfare sale, and other airlines followed right behind.

Savings range from $10 to $80 one-way on off-peak travel days (Tuesday and Wednesday) starting after 7-May.

The fifth time might be just what the doctor ordered for Air Canada. Three of their five attempts to raise airfares in 2007 quickly stalled. Air Canada did have some success with a airfare increases issued on 17-Jan, but not as much success as they might have hoped.

However, with the $4 (each-way) increase that started on 18-April, Air Canada has found support throughout the industry. The increase was matched by all of the legacy airlines in city pairs that overlap with Air Canada.

Previous attempts by legacy airlines (American, Continental, Delta, Northwest, United, and US Airways) to issue system-wide airfare increases have been thwarted by Southwest’s refusal to participate. This past Friday morning, though, Southwest gave the other airlines a break by raising fares by $2 each-way in approximately 40% of its city pairs. All of the legacy airlines quickly matched the increase over the weekend in city pairs where they compete with Southwest.

This is the second increase initiated by Southwest in 2007, and even though it is limited to $2 one-way* ($1 in 10% of Southwest’s city pairs), it applies to all advance purchase fares (walk-up, 3-day, 7-day, and 14-day). It also enables the legacy airlines to match the increase and raise bottom prices in all Southwest crossover city pairs.

Bankruptcy can directly affect the filing of new airfares. This has once again been made clear by the fact that Northwest Airlines has filed 14 million new U.S and Canadian airfares since November of 2004. American, on the other hand, has only filed 5 million new fares during that same time period.

The list below shows the number of new airfares airlines have issued since November of 2004. Northwest remains at the top of the list:

Northwest 13,973,210
Delta 12,043,643
United 11,418,474
Continental 6,460,105
US Airways 5,494,702
American 4,919,886
America West 2,300,296
Air Canada 2,101,923
Frontier 861,869
Alaska 807,888
Midwest 192,786