What did Conroy do with the CL-44?

Short answer

He converted it into the Conroy Skymonster (CL-44-O), a specialized 1960s cargo aircraft based on the Canadair CL-44 freighter with an oversized fuselage, designed to carry three Rolls-Royce RB.211 engines from Belfast to Palmdale, California. It first flew on 26 November 1969.

Published: November 5, 2026 · Updated: November 5, 2026 · Edited by Above Ten Thousand · Editorial policy

EI BND at Stansted (1986)Colin Cooke Photo (CC BY SA), vía commons

From the Guppy to the CL-44-O

John M. Conroy had previously founded Aero Spacelines, the company that created the Guppy series, aircraft designed to carry oversized cargo. The Conroy Skymonster (CL-44-O) was a specialized cargo aircraft from the 1960s based on the Canadair CL-44 freighter, with an oversized fuselage. It was conceived as a transport capable of carrying three Rolls-Royce RB.211 engines from Belfast, in Northern Ireland, to Palmdale, in California.

A conversion built in the open air

The transformation involved an enlarged fuselage. The nose section was built from foam coated in fiberglass, while the larger fuselage was built up with conventional aluminum structure. The work was carried out outdoors, under covered scaffolding, at Santa Barbara Airport, California. The aircraft first flew on 26 November 1969 with the US registration N447T.

A lost contract and a long career

In 1969, Conroy and the CL-44-O lost the contract for transporting the RB.211 to Saturn Airways, which offered the Lockheed L-100-30 Hercules. In 1970 the prototype was leased to Transmeridian Air Cargo, which named it "Skymonster". In 1978 it was bought by British Cargo Airlines. In 1982 it passed to HeavyLift Cargo Airlines, which re-registered it with the Irish registration EI-BND.