I would say lack of staff travel or significant incentives to book through Jet2 holidays is a lost marketing opportunity.
If you asked for a show of hands in the crew room for those who have booked a Jet2 holiday or flight in the last 12 months it wold probably be less than 10%. There are two issues with this;
Your staff have no real idea about the product, especially on the holidays side, when friends, family and colleagues ask, knowing that you work for the company. They can't say what an amazing holiday they had with the company and upsell the brand.
It doesn't look very good when most your staff holiday with all the competition instead!