Aye, they own like 1% more than Newcastle. Local councils own a stake in the airport, a total of either 49% or 51%. Each council owns a % in relation to their population. Because Newcastle only includes the city centre, the west end, and limited parts around the city centre, with North Tyneside, Northumberland, Gateshead, and South Tyneide all taking away from Newcastle's true population. Sunderland meanwhile accounts for the population of the whole of Wearside and parts of Durham. At the time of sharing the shares of the airport out this give Sunderland a higher population than Newcastle, although we all know that's not the case. As a result Sunderland council gained a slightly higher percentage of shares of Newcastle airport.
Since then Newcastle's population on it's own has now surpassed Sunderland's.
Interesting, cheers!