NATO says it has started round-the-clock surveillance of the air space over Libya, where government jets have been pounding rebel positions in an effort to defeat an uprising.
A NATO official said the first airborne warning and control plane went on patrol at 6.30am local time on Thursday morning.
He says each of the Boeing E-3 Sentry aircraft will remain over the Mediterranean for eight hours before being replaced by another plane.
NATO has 17 E-3s. Several planes are currently operating over Afghanistan.
The entire fleet is registered in Luxembourg, a country without an air force.
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NATO decided on Monday to provide the surveillance.
Orders to the E-3 squadron went out on Tuesday, said the official who could not be identified under standing rules.
