Virgin Blue has ordered a new generation of more efficient and environmentally friendly engines worth $US100 million ($136 million) to power its next batch of Boeing 737-800 aircraft.

The nine new aircraft, due for delivery between 2008 and 2010, will be powered by CFM International's CFM56-7B engines.

Virgin's planes also use engines made by CFM, a joint venture between Snecma and General Electric.

The engines will be modified with a "tech insertion" providing lower maintenance costs, improved nitrogen oxide emissions and better fuel burn.

The tech insertion is scheduled to be certified by regulatory authorities in the third quarter of this year and includes improvements to the high-pressure compressor, the combustor and the high- and low-pressure turbines.

"One of the key competitive advantages for Virgin Blue is its modern fleet of Boeing Next Generation 737 aircraft with the latest technology, and that obviously extends to the engines attached to those aircraft," a Virgin spokeswoman said.

"Technological advances are critical in helping us maintain a low cost base and CFM's ongoing engine enhancements allow Virgin Blue to be economically savvy in terms of fuel burn and long-term maintenance costs as well as (being) environmentally friendly."

Meanwhile, Regional Express said an agreement with Adelaide Airport meant new arrival procedures would take effect from July 10. Arriving passengers will be bussed from the aircraft directly to the Rex Arrival Terminal, formerly the airport's international terminal building, to avoid a mandated security check on arrival. A deal on the new procedures was brokered after a slanging match between the airline and the airport over the $260 million new terminal.

Rex, which represents about 5 per cent of the airport's daily traffic, had received hundreds of complaints about a 700m walk from the check-in desk to planes as well as the need to pass through in-bound security checks.

Rex also announced additional flights to Port Lincoln in South Australia after the withdrawal of Qantaslink.

It will operate four extra return flights each week between Adelaide and Port Lincoln from July 17 and add another three return flights each week from August 14.