With the JR Tokaido Shinkansen Line now stopping at Shinagawa, airlines are bracing for cutthroat competition with the speedy rail service between Tokyo and Osaka.

The new stop will definitely be handier for travelers transferring to local trains in southwestern Tokyo, but many experts predict the increased frequency and new fare cuts for Nozomi bullet trains -- the fastest service offered by Central Japan Railway Co. (JR Tokai) between the two cities -- will pose the greatest threat to domestic air carriers.

"The shinkansen's existence has always been a threat to airlines," said Ikuo Kojima, an economic journalist well-versed in transportation issues.