Corsair
I think you will find that it was when JB mistook Monaghan for Amargh at night, and would have delivered the mail there if he had found a landing site.
Similar to the Lynx with nitesun.
When told by St Angelo Buzzard to move further west as he was shining the light across the border. The Air Gunner denied it and said they were over Rosslea.
Buzzard repeated 'Move west!! the man at the window holding a phone in the middle of your nitesun beam is the Garda at Cloones and can confirm you are in the South'.
The Lynx hastily headed west