KUALA LUMPUR - Malaysia will host the most sombre race in its 15-year Formula One history this weekend as the mystifying MH370 plane tragedy overshadows an incident-packed start to the season. With aggrieved champions Red Bull this week issuing a veiled threat to quit, and new rules prompting an immediate shift in the pecking order, Formula One has rarely been so eventful. But the initial focus will be off the track as Malaysia mourns the 239 people aboard ill-fated Flight MH370, with planes and ships scouring the treacherous Indian Ocean for wreckage.The Sepang racetrack is geographically close to Kuala Lumpur's international airport, where the Malaysia Airlines flight took off on March 8 and vanished from radar screens shortly afterwards. And its proximity to the unfolding drama was illustrated when more than 30 relatives of missing passengers had to shift to other hotels to make way for F1-related bookings made in advance. A major F1-related concert featuring Christina Aguilera at Kuala Lumpur's Twin Towers has been cancelled as a mark of respect, and organisers may also call off an air show at the track.Sepang CEO Razlan Razali told AFP that despite the tragedy, attendance numbers looked set to be on track, with about 30 percent of race-day tickets already sold. But Ram Sithambaram, owner of an F1 outlet at the airport, said sales of tickets and merchandise had been poor for the race, first staged in 1999. "In the past one week we sold only about 50 tickets. In comparison last year around the same period we sold about 1,000 tickets," he said. "We are paying a high price for the MH370 tragedy... we hope for a miracle that ticket sales will surge in the next few days." Drivers will pay their own tributes, with Mercedes' early championship leader Nico Rosberg tweeting: "all my prayers go to friends & families of the passengers on # MH370". But mostly their thoughts will remain on the tough job at hand as all teams absorb widespread changes involving hybrid power, fuel limits and the new, and controversially quiet, turbocharged V6 engines.Red Bull were incensed after a wipe-out in the opening race in Australia when four-time defending world champion Sebastian Vettel retired early and Daniel Ricciardo was stripped of second place over the new fuel rules. Team owner Dietrich Mateschitz told an Austrian newspaper "there is a clear limit to what we can accept" when asked under what circumstances Red Bull would quit F1.The quiet new engines, criticised by F1 supremo Bernie Ecclestone among many others, will hardly lift the mood at the track as a sedate hum compared to vacuum cleaners replaces the previous deafening shriek. Rosberg's Mercedes made all the running in Melbourne but his team-mate Lewis Hamilton, starting from pole position, lasted just a few laps, underlining the unpredictability of the new cars.McLaren were one of the big winners in Australia. Denmark's Kevin Magnussen finished second in his first F1 race and Jenson Button was third, putting the team on top of the constructors standings. But Vettel, seeking to emulate the stricken Michael Schumacher's five consecutive world championships, will want to recover quickly from his forgettable outing. "We still have a lot of work to do with the car but it was encouraging to see that our pace was better than expected in Australia," said the 26-year-old German. "Hopefully we can build on that and start collecting some strong points in the next two races."