Concerns about 27 120 kg sumo wrestlers on a plane prompted an "unusual step" to be taken by Japan Airlines.

The airline had concerns that the two planes the sumo wrestlers would initially fly would not be able to carry enough fuel due to weight restrictions.

The concern about fuel capacity began when staff learned late on Thursday that the passenger lists included sumo wrestlers, who weighed an average of 120kg - well over the 70kg average.

"It is extremely unusual for us to operate special flights due to the weight on the aircraft," a Japan Airlines spokesman told regional newspaper Minami-Nippon Shimbun.

There is no minimum weight requirement to become a sumo wrestler, but the ancient sport is dominated by heavy men. ?rora, a Russian-born sumo who retired in 2018, is the heaviest of all time - 292.6 kg at his peak.