Embattled carrier Qantas was forced to cancel or delay more than 70 flights on Monday despite aircraft engineers calling off strike action after unions said the airline threatened to withhold pay. Line maintenance engineers, who check aircraft on the tarmac, were planning to stop work for four hours as part of a labour dispute in Sydney, Brisbane and Melbourne. But just hours before walking off the job the Australian Licenced Aircraft Engineers Association (ALAEA) cancelled the strike, saying Qantas management threatened to withhold up to seven hours\' pay for the time not worked. \"The airline is playing dirty pool with our members by threatening them for taking lawful industrial action,\" ALAEA Federal Secretary Steve Purvinas said. \"To ensure our members are not unfairly disadvantaged by Qantas management\'s last-minute curve ball, we have decided to reassess our position on today\'s planned action. \"We are currently seeking legal advice and if necessary we will launch legal action against the airline for unlawful adverse action against our members,\" he added in a statement. Despite the backdown, Qantas said it was too late to change flight plans for the day and that the cancellations and delays announced earlier would remain. \"They have called off the strike late and we have plans already in place. Unfortunately, it is too late to relook at those plans,\" a Qantas spokeswoman said. The Qantas website showed 35 domestic flight cancellations and another 34 services delayed or brought forward. Several international flights will also be affected, with delays of more than two hours on some services to London via Bangkok and Singapore, Frankfurt via Singapore, and to and from Auckland. Unions are locked in protracted contract talks over pay and conditions with Qantas, which has said it will slash 1,000 jobs as part of its new Asia focus, with baggage handlers and other ground staff also striking in recent weeks. On Friday, Australian police said they were investigating alleged death threats against chief executive Alan Joyce, while the airline has said managers had been sent menacing letters and strike-breaking workers bullied.