In September 2006, the Saudi government signed a contract worth £2.5 billion (US$4.7 billion) with BAE Systems to upgrade up to 80 RSAF Tornado IDS aircraft to keep them in service until 2020. The first RSAF Tornado was returned to BAE Systems Warton in December 2006 for upgrade under the "Tornado Sustainment Programme" (TSP) to "equip the IDS fleet with a range of new precision-guided weapons and enhanced targeting equipment, in many cases common with those systems already fielded by the UK's Tornado GR4s." In December 2007, the first RSAF aircraft to complete modernisation was returned to Saudi Arabia. Starting from the first week of November 2009, Saudi Air Force Tornados, along with Saudi F-15s performed air raids during the Shia insurgency in north Yemen. It was the first time since Operation Desert Storm in 1991 that the Royal Saudi Air Force participated in a military operation over hostile territory. Saudi Air Force Tornados are playing a central role in Saudi-led bombing campaign in Yemen. On 7 January 2018, Houthi fighters claimed to have shot down a Saudi warplane which was conducting air-raids over northern Yemen. According to Saudi reports, the downed aircraft was a Tornado of the Royal Saudi Air Force which was on a combat mission in the skies over Saada province in northern Yemen. Saudi reports said that it was lost for 'technical reasons' and that both crew were rescued. In the night of 14 February 2020, a Saudi Tornado was shot down during close air support mission in support of Saudi allied Yemeni forces in the Yemeni Al Jouf governorate by Houthis. On the day after, the Saudi command confirmed the loss of a Tornado, while video evidence was released showing the downing using a two-stage surface to air missile. Both pilots ejected and were captured by Houthis. RAF IDS (interdictor/strike) variants were initially designated the Tornado GR1 with later modified aircraft designated Tornado GR1A, Tornado GR1B, Tornado GR4 and Tornado GR4A. The first of 228 GR1s was delivered on 5 June 1979, and the type entered service in the early 1980s. The Tornado GR1B was a specialised anti-shipping variant of the GR1, replacing the Blackburn Buccaneer. 26 aircraft were converted and were based at RAF Lossiemouth, Scotland. Each aircraft was equipped to carry up to four Sea Eagle anti-ship missiles. At first the GR1B lacked the radar capability to track shipping, instead relying on the missile's seeker for target acquisition, later updates allowed target data to be fed from aircraft to missile.