The visitors put four past Guernsey goalkeeper Jordan Kelly, and despite some good chances Guernsey struggled to find a way through and were made to pay for their mistakes.
Leon Meakin’s youthful side found themselves trailing as an excellent strike from the Fleet Air Arm's Ben Aldos found the top corner.
Minutes after that opener, Kelly was tested by Aiden White, but the Guernsey goalkeeper was able to collect his low drive towards the bottom corner.
The hosts had a few chances, but it was the visitors doing most of the attacking, at least until the last 10 minutes of the first half, during which the hosts had a flurry of chances but failed to cause Sam Kellet too many problems.
In the 43rd minute, White set up Aldos to head in his and the Fleet Air Arm’s second, making their lead more comfortable at half-time.
But at the end of the first half Guernsey had squandered a great chance as a goalmouth scramble ended with Jake Martin hitting the post.
The second half provided no relief for Guernsey, with Aldos completing his hat-trick as early as the 46th minute.
On the hour mark, he went close to scoring a fourth. After battling against the young Guernsey defenders, the Fleet Air Arm no. 9 broke through and went one-on-one with Kelly, but his effort skimmed the crossbar.
Minutes later, Guernsey had a good chance, as Sam Cooley got on the end of a good ball into the penalty area, but his header was just off target.
In the 75th minute, James Plumer broke through and slotted the ball past Kelly and into the bottom corner, making it 4-0.
TEAMS
Guernsey: Kelly, Cleal, Mourant, Sylvester, Tyrrell, Roberts, Martin, Beddow, Torode, Le Poidevin, Dorrian. Subs: Vance, Robilliard, Cooley, Guimaraes, Kelly.
Fleet Air Arm: Kellet, Grett, Barron, White, James, M Upchurch, O’Neil, L Upchurch, Aldos, Powell, Sutton. Subs: Alderson, Bond, Barlow, Plumer.
