International air travellers were warned to turn up early for flights out of Australia and to expect possible delays Thursday after customs officers launched a 24-hour strike over pay. Overseas-bound passengers braced for the prospect of long queues as management manned the customs barriers at Sydney, Melbourne and Perth international airports after employees downed tools at midnight. But officials said they did not expect arriving delegates to the Commonwealth heads of government summit in Perth to be caught up in the dispute, as VIPs are whisked through under special customs arrangements. \"Our key message for today is for anyone in the travelling public who\'s got a flight out of an international airport to get there in plenty of time to get through the customs and border protection processes,\" the agency\'s acting deputy chief executive, Jan Dorrington, said. But she said no major delays had occurred at the three key airports by mid-morning, although she warned the situation could change. \"We have very well planned contingency arrangements. We have very carefully calculated the number of staff we need on the primary line and the number of staff required for other tasks in airports in particular.\" However the union that represents customs workers said long queues were forming in the three key airports. \"We are getting some reports in that there are some delays already and that they vary from place to place,\" Dermot Browne of the Community and Public Sector Union told AFP. The latest in a series of customs strikes over the past two months came after staff rejected a three percent per year pay rise saying it was below Australia\'s 3.5 percent annual inflation rate. \"We would much prefer to resolve this dispute through negotiations than taking industrial action,\" Browne said, adding the latest strike reflected customs workers\' rising level of frustration. \"We remain confident that we will get a deal, but it\'s just got to be a deal that won\'t leave people worse off than they are,\" he said. The Queen will on Friday open the Commonwealth summit in Perth, where 54 leaders of the global grouping and their entourages are already gathering. But Dorrington said that last minute arrivals of dignitaries would not be affected by the strike.