The Japanese Grand Prix, scheduled for next weekend, April 23-25, has been postponed because of the disruption in air travel caused by volcanic activity in Iceland.The second round of the MotoGP World Championship, to be held at Twin Ring Motegi, will now be held the weekend of October 3. That makes it the first of three races in a row; the Malaysian GP is the following weekend, with the Australian GP at Phillip Island falling on October 17.An e-mail from IRTA said that "Due to the continuing uncertainty about the availability of air travel the decision has been taken to cancel the Japanese Grand Prix on 25 April."Though flights from the U.S. to Japan are unaffected, most air travel in Europe, and all flights in the UK, have been canceled for the fourth day, with no end in sight. Flights in southern Europe were originally less affected, but the ash cloud is now drifting south and east. Without knowing when flights might resume, Dorna, in consultation with the track and the teams, had no choice but to postpone the race.The Eyjafjallajoekull volcano in Iceland erupted on Wednesday, sending a cloud of ash into the atmosphere into some of the same altitudes where commercial airlines fly. The International Air Transport Association estimates its costing airlines $200 million a day in lost revenue. The volcano is still erupting, though less violently than originally.