When the dust settled following the robust legislative session this year, $7 million had been set aside for the Minnesota Department of Transportation to buy two planes.

Airplanes? For the state agency that tends to Minnesota's vast system of roads?

As Mike Hartell, assistant director of MnDOT Aeronautics, explains it, two of the four airplanes now owned by MnDOT need to be replaced. Both are single-engine Beechcraft Bonanzas — one is 45 years old, the other is 18 years old, he said.

MnDOT says the duo primarily serve as "heavy-duty pickups in the sky" largely used to maintain a network of critical aviation navigational systems (or NAVAIDs) that commercial aviation services and private pilots depend on. There are 133 public airports in Minnesota, two of which are seaplane bases in the Northwest Angle and at Crane Lake.

When not being used for maintenance duties, the aircraft are deployed for airport, heliport, seaport and other inspections, many of which are required by the Federal Aviation Administration.

"For everyday use, they're outside of their useful life," Hartell said, noting that it's increasingly difficult to repair the aging aircraft.

MnDOT is now preparing a bid for two newer single-engine turbo prop airplanes as replacements. These planes will be better equipped to ferry technicians, equipment and tools around the state to maintain NAVAID systems, Hartell said.

The agency is looking for winter-capable aircraft with updated avionics that can accommodate two pilots, four passengers and up to 600 pounds of cargo.

While the utility airplanes also provide air transport for MnDOT and other state employees for official business, the department's two additional King Air airplanes usually handle that job. All of MnDOT's planes are stationed at the St. Paul Downtown Airport.

"We heavily depend on these airplanes," Hartell said.