Guernsey States has agreed to the compulsory purchase of a field and the closure of a road to allow an extension to the airport's runway.
The 3.71 vergees (6,000 sq m) field belonging to the Le Messurier family and La Mare Road are needed to extend the runway's safety area.
An attempt to force the States to look at the planning issues around the project failed.
Deputies rejected the move, which would have delayed their other decisions.
The debate had already been delayed by one month, to allow a report on alternative options for improving the runway safety area to be released.
The £81m project also involves the reconstruction of the hard surfaces and the replacement or refurbishment of the drainage system, airfield lighting and other key operational systems. It was approved in 2009.
The Public Services Department had warned another delay would cost an additional £2.5m.