I would say they are undervalued if the share price of 48.5p is based upon an estimated value of £68 million.
In Jet2.com alone, they have a sizeable fleet of aircraft valued at IMHO:
14 x B737-300 148 seat Pax only- £2 million each = £28 million
7 x B737-300 QC Pax/Freight Convertibles- £3 million each= £21 million
8 x B757-200 235 seat Pax aircraft- £5 million each = £40 million
Therefore, the aircraft alone are worth at least £89 million, add to that their holding of spares, the simulators, the Jet2.com brand, property, slot allocations, the Fowler Coolchain company, network & assets... £68 million seems very, very cheap.