The US Air Force (USAF) has issued a stop-work order to the team of Sierra Nevada Corporation (SNC) and Embraer on the recently awarded $355m Light Air Support (LAS) contract for the Afghan Air Force, following a lawsuit filed by Hawker Beechcraft.

Hawker sued USAF in the US Court of Federal Claims over its exclusion from the LAS competition in November 2011, demanding an explanation from the US Government Accountability Office (GAO) over the decision, which was later dismissed. However, Air Force officials continue to defend the controversial award and said the stop-work order is a precautionary measure to accelerate the process of sorting out the claims made by Hawker.

Hawker also claimed that it had worked for two years with the service to develop the aircraft’s parameters and invested more than $100m for the LAS competition. The company had proposed an armed version of its T-6 trainer, the AT-6, for the contract worth nearly $1bn to supply up to 55 LAS Counter Insurgency aircraft for the Afghanistan National Army Corps.

Eventually, the USAF awarded the firm-fixed-price contract to the Sierra Nevada and Embraer team for the supply of 20 A-29 Super Tucano light-attack aircraft by 30 April 2014. The contract also includes delivery of ground training devices (GTD) including simulators and planning stations, in-field logistic support, as well as pilot and maintenance training.

USAF spokesman lieutenant colonel Jack Miller said: "The competition and source selection evaluation were fair, open and transparent. The Air Force is confident in the merits of its contract award decision and anticipates that the litigation will be quickly resolved."

The A-29 Super Tucano, designed for counterinsurgency missions, will be used by the USAF to conduct advanced flight training, aerial reconnaissance and light air support operations.