The RAF says a squad of its American-made Chinook helicopters is likely to be a daily sight in the skies over Lancashire and the North West for the next two weeks, as pilots and crewmen take part in "essential training".
It says three of its Chinook helicopters will be operating from RAF Woodvale, an air base near Southport, whilst training missions take place across the region.
The training exercise - codenamed KUKRI DAWN - will take place from Monday, June 21 to Friday, July 2.
The aircraft - which can carry up to 55 troops - will be flying between 9am to 5pm, with no night flying expected.
They have already been spotted flying across parts of Preston and South Ribble today, with sightings over Worden Park in Leyland this morning (Tuesday, June 22).
The RAF says the public should not be alarmed at the sight of the large helicopters, which are likely to operate in pairs with some training taking place in urban areas.
It says the tandem training missions in urban environments is essential practice for the crews on the Chinook training course, which qualifies pilots and crewmen to operate the Chinook helicopter for operations in the UK and overseas.
The aircraft will primarily be operating in the areas around RAF Woodvale, which could include Lancashire, Liverpool and Manchester.
An RAF spokesman said: "The exercise is the final part of the operational flying phase of the Chinook training course run by 28 Squadron based at RAF Benson; the Operational Conversion Unit for the Puma and Chinook Forces.
"The course qualifies pilots and crewmen to operate the Chinook helicopter on operations within the UK and when deployed overseas.
"This is essential training providing key skills that will be required when they graduate from the Operational Conversion Unit and are posted to a front-line helicopter squadron.
"The operational phase of the course is the culmination of months of training by the students and, all being well, will see them return to RAF Benson ready to graduate.
"They will be flying during RAF Woodvale’s normal operating hours of 0900 to 1700hrs, with no night flying expected.
"At times, the Chinook helicopters may be operating in pairs and may also train in urban environments, both of which are key skills for the crews.
"RAF Woodvale provides an excellent forward operating base for the Operational Conversion Unit. It also provides additional support to the training being undertaking by introducing the crews to operating in unfamiliar surroundings and a different environment."
The UK Government has recently agreed to invest £1.4 billion into modernising its Chinook fleet over the next 10 years. The deal will see British forces benefit from another 14 of the latest iconic heavy-lift helicopters, in addition to the 60 Chinooks already in service.