mowing the lawn

mowing the lawn
 n.— «Maritime patrol planes fly a grid pattern over the search area, guided by GPS. They fly in parallel swaths over the ocean, in a process that pilots refer to as “mowing the lawn.” Flying at an altitude of 600 metres or less, pilots and crew watch for surface debris and fuel slicks.» —“How the hunt for the missing airliner will unfold” by Peter Cheney Globe and Mail (Canada) June 3, 2009. (source: Double-Tongued Dictionary)