Passengers on an AirAsia flight from Kuala Lumpur to Singapore will be the first to land at Changi Airport's new Terminal 4 tomorrow.

The return flight will also take off later from the terminal, The Straits Times has learnt, as part of trials to ensure smooth operations when T4 officially opens later this year.

Systems and processes have been rigorously tested since October last year at T4, which will feature many firsts here, Changi Airport said.

For example, T4 will be the first passenger terminal at Changi to deploy body scanners for security screening, following several trials at the other terminals.

The new facility will also rely heavily on self-service options to reduce reliance on manpower and harness new technologies.

From check-in to bag tagging, as well as bag drop, immigration checks and aircraft boarding, there will be no contact with airport staff for most passengers, except during security screening.

To ensure that it is the same person moving through the different processes, T4 will feature - for the first time at Changi - a facial recognition system which will capture the passenger's photo at the different stations.

In some cases, passengers with visa requirements, based on their nationalities and where they are flying to, will be directed to manned counters for their documents to be checked.

While self-service options have been rolled out progressively at Changi since 2015, T4 will be the first to offer travellers a start-to- end automated system.

So far, more than 100 trials have been conducted involving more than 2,000 volunteer participants and 1,000 airport employees, Changi Airport Group's head of the T4 programme Poh Li San said during a media preview yesterday.

Apart from self-service options, the systems and processes being tested include security screening, GST refund, baggage reclaim, ground transport and way-finding, as well as passenger and baggage transfers.

Test flights - which start tomorrow - will also provide valuable opportunities to simulate real flight situations with actual passengers. They will create a more realistic operating environment and enable the airport to identify gaps which might not have surfaced earlier, Ms Poh said.

AirAsia's Singapore chief executive Logan Velaitham said: "The test flights will not just benefit our staff, but also give our customers an idea of what they can expect when we move our operations to T4."

Apart from the AirAsia group, Cathay Pacific, Cebu Pacific, Korean Air, Spring Airlines and Vietnam Airlines will also operate from T4 when it opens.

Together, the airlines serve an estimated eight million passengers at Changi Airport each year, which is about half the total handling capacity of the new terminal.

Even as extensive testing is being done to ensure all goes well, the airport is prepared for some teething problems when full operations are launched, Ms Poh said.

"We have devised contingency and backup plans that will kick in when necessary so that passengers can still go through the entire check-in and departure process very smoothly," she said.