YOUR article referring to low flying jets being sighted over the region on the morning of January 17 (LET, January 19) was not entirely correct.

The skies over East Lancashire are a busy intersection of high-level routes along which aircraft movements are monitored and regulated by controllers on the ground.

What observers were witnessing on Saturday is not uncommon during morning and evening peak arrival times at Manchester International. At these times large passenger jets can often be seen at much lower altitude flying a circular holding pattern or 'stack,' as it is known.

To cope with the extra volume of traffic, Manchester Approach Radar employ a 'stack' over our region, some 30 nautical miles out from the main runway.

Often a number of aircraft can be seen circling in this holding pattern with a minimum safe vertical separation of 1,000 feet as they await their designated landing slots.

Systematically, flights are 'bled' off the base of the stack and safely guided down by radar and electronic means to touch down at Manchester.

On Saturday morning, due to weather conditions at Manchester, the clear skies over Blackburn were populated by a number of large jets awaiting clearance. One of these was an Air Atlantique 747 circling at about 10,000 feet. The huge size of the Jumbo making it appear to be much lower.

To the casual observer, seeing this juggernaut of the skies circling at approximately five minute intervals, it may have seemed like a number of planes overflying the town.

DAVID L COGGINS, Lammack, Blackburn.