Wreckage thought to be that of a missing light aircraft was found off the coast of Blackpool, the RNLI said.
One of the six lifeboats involved in the search operation found it in the sea off South Shore, Blackpool.
Police, the coastguard and lifeboats were searching for a two-seater light aircraft which went missing with two men on board.
Blackpool RNLI spokesman Paul Parton said: "The lifeboat crews had been searching for almost two hours when the wreckage was discovered quite close to shore.
"The search for survivors will continue. The sea is calm but visibility is poor due to fog, which has made the search more difficult than it might otherwise have been.'
The six RNLI lifeboats were launched. The aircraft was believed to have been travelling from Exeter to Blackpool.
A search was launched after air traffic control reported that a small aircraft, a Warrior PA28, may had gone down, Liverpool Coastguard said.
A spokeswoman said radar contact was lost with the light aircraft at about 5.15pm.
A spokeswoman for the Maritime and Coastguard Agency (MCA) said two coastguard rescue teams were searching the shoreline with police. A rescue helicopter was scrambled from RAF Valley, in Anglesey.
The PA28 is a four-seater light aircraft often used for pilot training or private travel. The single-engine aircraft has a 10.6m (35ft) wingspan, is capable of speeds of up to 146mph and has a range of 736 miles (1,185km).
