The Blues’ Checkatrade Trophy final allocation was snapped up within eight days – including just one day on general sale.
The March 31 fixture will attract more than 80,000 supporters, with opponents Sunderland having also sold their share.
Pompey’s previous highest attendance in the oft-criticised competition was 3,138 against Spurs under-21s in November.
Yet the Fratton faithful will be packing Wembley for the final.
And Jackett has marvelled at the strength of support demonstrated by Blues followers.
He said: ‘What a fantastic response, it shows what a Wembley appearance means to the Portsmouth supporters.
‘For myself, the staff and the players, to see such fantastic backing is exciting. There's no doubt that when you sell 40,000 tickets in that short space of time it shows the great potential of the club.
‘Portsmouth haven’t been to Wembley since 2010, so there’s great enthusiasm for it.
‘Inside the club it is much appreciated and good to see.
‘Everybody told me a sell-out would be there. Everybody told me that would be the possibility – and it’s fantastic to see.
‘It's a unique game for this particular competition, both sides have sold out their allocation, perhaps they’ll be between 80-85,000 present, which is great.
‘In earlier rounds, the Remembrance commemoration held before the Spurs under-21 game was very well attended and generally the competition picks up pace as you go along.
‘As you start to progress there is a possibility of success, then suddenly you have the semi-final and it’s a great chance to get to Wembley – one I’m pleased to say we took.’