Its air defence consists of 30 McDonnell Douglas F/A-18 Hornets and 53 Northrop F-5 Tiger IIs (110 purchased in 1978–85). The F/A-18 pilots are career military; the F-5 pilots however are reservists (mostly air- or freight-liner pilots with F-5 rating). During reserve duty periods they are assigned to military duties refreshing their operational live flying training and rating. In 2008, the Swiss F-18 component reached its 50,000 flight hour milestone. Due to the RUAG Upgrade 21 (UG21) programme between 2004 and 2009 and the Mid-Life Update (MLU) its operational lifecycle will be guaranteed until 2022.