Saturday's official opening of the Ngong Ping 360 cable car may be postponed, its operator said yesterday after 500 passengers on a trial run were left stranded in mid-air for two hours. The stoppage follows a similar one on Friday morning, when failure delayed the start of the service by 45 minutes and hundreds of elderly and disabled guests were forced to wait in sweltering heat. Yesterday's stoppage happened at about 3.30pm. About 5,000 MTR employees and their families had been invited to try out the ride. Among those trapped was MTRC Staff General Association chairman Mak Pui-tung. 'At first they told us the stoppage was just a test, but later they said there had been a malfunction in the system. They only said it was safe inside the cable car and nothing about what we should do,' the union leader said. Another rider, whose cable car stopped just minutes before reaching Tung Chung station, said the emergency phone in the cable car did not work properly. During the stoppage there were long queues outside Ngong Ping and Tung Chung stations. The operator had to request extra bus services between the two stops. Last night, operator Skyrail-ITM apologised for the stoppage and blamed it on a failure of the system that maintains spacing between the cable cars. Managing director Bill Calderwood said that at no time was passengers' safety compromised. 'In the event of a stoppage such as this, passengers are safest where they are, in fully enclosed cable cars, and the communication systems in place allowed us to keep all of them informed of the repair progress,' he said. 'We fully understand the delay was frustrating, but it was better for all concerned to remain safely on board until the cable car operation could be resumed.' A trial run planned for today has been cancelled to allow engineers to conduct further tests. Mr Calderwood said the test results would determine whether they had to delay commencement of the service on Saturday. A decision is expected by the end of today. Lau Kong-wah, chairman of the Legislative Council's transport panel, said the operator had to put passengers' safety first, adding that the opening should be delayed if the engineers picked up problems. Earlier this month, gale-force winds exceeding 90km/h near the site of the Big Buddha on Lantau Island disrupted the cable car system on the first day of trials. The 5.7km cable car journey is expected to attract 1.5 million visitors in its first year of operation.