The plans include a new multi-story car park and knocking down the 1937 arrivals building.
The building, which has already lost two floors due to safety concerns, has been called "unsafe" by airport bosses.
But Christopher Scholefield, from Save Jersey's Heritage, said plans to demolish the Art Deco terminal would be a loss to the island.
"Why is it that the interesting, genuine, historical, architectural artefact has to be knocked down in order to replace it on virtually the same footprint?
"If we ended up with what they're going to build... it won't be horrible, but we'll have something that's not genuine anymore."
Group chief executive officer of Jersey's airport and harbours, Doug Bannister, said: "It's actually not so original because it's been added to year after year... over the decades.
"It's an obstacle and what that means is it's too big and too close to the runway. It's currently unsafe."

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The 29-year-old was overlooked for their triumphant Six Nations campaign after starting in the 2015 World Cup.
The surgery ruled him out of contention for the tour to Australia in June.
"You always have to keep the goal there to get back in the England side. I don't think you can ever lose sight of it," he told BBC East Midlands Today.
"Because I was injured, yes you do end up doubting yourself a little. But you soon dust yourself down, get back here, train again and then you are ticking along again.
"I've always had determination, but there is probably a bit more there now to prove people wrong and prove to myself that I'm good enough."
Youngs, capped 22 times, was not selected after Eddie Jones took over as national boss, with the Australian naming hooker Dylan Hartley as his captain.
Saracens' Jamie George and Exeter's Luke Cowan-Dickie played as replacement hookers during the triumphant summer tour to Australia.
"They had a great summer tour, 3-0 in Australia is very special," Youngs said.
"It's never great not being selected, but there is no point moping about because you need to be training hard. I'm not one to mope, I just say 'fair enough, I understand' and then go off and work on things I need to work on.
"The back injury was probably the worst thing, because I couldn't prove anything.
"If I get the phone call great, but I'll concentrate on getting fit, playing and leading by example for the club."
Youngs said recovering from surgery was "a dark time" as Leicester's bid for European Champions Cup and Premiership glory ended at the semi-final stage of both competitions last season.
While Leicester reached the Premiership play-offs for a 12th straight season, it was the third successive time they fell short of a spot in the final.
Youngs will mark his recovery by taking over as Leicester club captain.
"It's a huge honour and a big job to do," he said.
"I want to get Leicester back to where we should be really, and where we are striving to be. We have been in three semi-finals now and lost all three.
"We need to finish in the top two this year and push for that and reach a final. That is what we are pushing for in all competitions."

Graham Dwyer, 42, from the Foxrock suburb of south Dublin, pleaded not guilty to the murder of Elaine O'Hara.
The remains of Ms O'Hara, 36, were found in the Dublin mountains on 13 September 2013.
She was last seen on 22 August 2012, the day of her alleged murder, near Shanganagh cemetery in south Dublin.
The judge said 40 days of evidence, stretching back over five years, boils down to what happened in the three hours after Ms O'Hara vanished.
He told the seven men and five women they could take as long or as short a time as they needed to reach "a conscientious and properly considered verdict".
Designs for redeveloping an airport "remove" its Art Deco past, a heritage campaigner has said.
[NEXT_CONCEPT]
Leicester Tigers hooker Tom Youngs refuses to give up on an England recall, despite admitting he doubted himself after undergoing back surgery.
[NEXT_CONCEPT]
The jury in the trial of an architect accused of murdering a childcare worker in the Republic of Ireland has retired to consider its verdict.