German insolvency administrators have impounded a Boeing 737 of the Royal Thai Air Force at Munich airport, after the Asian nation's administration allegedly failed to make payments for a motorway project near Bangkok.

The government twinjet, a 1995-vintage 737-400 (registration HS-CMV), is frequently piloted by crown prince Maha Vajiralongkorn, according to the Neu Ulm-based administrators Schneider, Geiwitz & Partner.

Administrator Werner Schneider is leading the proceedings for Walter Bau, a construction company in Augsburg which became insolvent in 2005 and which was involved in the building and operation of a 26km (16mi) toll motorway between Bangkok and Don Muang airport.

Schneider is seeking a payment from Thailand's government of more than €30 million ($42 million).

Walter Bau merged with DYWIDAG in 2001, which built the motorway more than 20 years ago and became a shareholder in the project. This stake was sold back to the Thai government in 2007 after "a multitude" of contractual agreements had not been honoured on the latter's part, the administrators claimed.

The impounding, which took place on 12 July, was sanctioned by a court in Berlin.

The search for the aircraft proved to be laborious and needed to be done discreetly to avoid any potential warning for the Thai government. However, Schneider had some previous experience - in 2005 he impounded an aircraft of Lebanon's Middle East Airlines in Istanbul.

Whether Thailand's governmental 737 will be sufficient to redeem the debt remains to be seen. According to Avitas, the twinjet has a base market value of $9.6 million. However, with the large number of parked Classics, the current market value has dropped to just under $6 million.

Thai government officials could not immediately be reached for comment.

Source: Air Transport Intelligence news