Measures to prevent aircraft from making runway incursions may not have been suitably shared with the Japan Coast Guard, whose plane was involved in a deadly collision at Tokyo's Haneda airport, information revealed by the transport ministry suggested Thursday.

In the Jan. 2 collision between the coast guard's aircraft and a Japan Airlines jetliner, experts have pointed out the possibility that the former mistakenly entered the runway. Five of six people aboard the coast guard plane died and its captain was severely injured, while all 379 passengers and crew on the commercial aircraft escaped.

Following a series of unapproved entries by aircraft at Japanese airports, including Osaka, Kansai and Chubu airports between September and November of 2007, the ministry and relevant parties launched a team to prevent recurrences, but the coast guard was not part of it.