the height of the operation a peak of 33 tanker aircraft and 600 troops deployed to Lajes. Soon after the Gulf War ended, Lajes command changed from Air Mobility Command, to Air Combat Command. In 1993, squadrons 503 and 752 are merged in a single mixed unit operating both C-212 and Aérospatiale Puma, the 711 Squadron "Albatrozes" (Albatrosses). The resident Portuguese 711 Squadron was deactivated on 30 November 2006. With this act the long-serving Aerospatiale Puma was retired from service. The Puma helicopters were replaced by the modern AgustaWestland AW101 Merlin: the Portuguese government purchased twelve units for SAR, CSAR and Fisheries enforcement. Air Base No.4 received three Merlins on permanent detachment from Esquadra 751 "Pumas" from Air Base No.6 at Montijo, near Lisbon. They saw immediate service starting 1 December 2006. However, maintenance problems developed in the next coming months which, coupled with a shortage of spare parts from the manufacturer, led to such a low serviceable rate forcing the Portuguese Air Force to pull the Merlin from service in the Azores. The last Merlin flew back to Montijo on 19 March 2009. In order not to compromise the SAR mission, the Portuguese Air Force decided to reactivate the Puma fleet: in July 2008 a formation of four Puma helicopters made the trans-Atlantic crossing from Beja to Lajes via Porto Santo Airport on Porto Santo Island and Santa Maria Airport on Santa Maria Island. Beginning in 1997, large scale fighter aircraft movements under the new USAF operating concept known as the Air Expeditionary Force (AEF) filled the Lajes flightline. Lajes also has hosted B-52 Stratofortress and B-1 Lancer bomber aircraft on global air missions, and also supported many routine NATO exercises, such as the biennial Northern Viking exercise. Lajes Field services aircraft from various nations, including Belgium, Brazil, Canada, Colombia, Denmark, France, Germany, Greece, India, Israel, Italy, the Netherlands, Pakistan, Poland, Qatar, Russia, Spain, Sweden, the United Kingdom, and Venezuela. The airfield was an alternative landing site for the NASA Space Shuttle orbiter and also now plays as the number one diversion airport for medical or mechanical emergency diversion situations for all types of aircraft. An annual average of 50 aircraft of all types divert to Lajes as a mid Atlantic safe haven. 2000 – present In 2009 Lajes provided rescue support of shipping lanes across the Atlantic, a safe haven for medical or mechanical emergency situations in aircraft