UA spending night at BRU?

[A330]

Hi,
I just arrived in BRU shortly after 21:30 on SK. While taxiing to the gate, I saw a UA aircraft parked. Could not see clearly (it was already snowing) but seemed to be a 777. It was positioned close to former C pier (my flight landed on runway 19).
Why is the aircraft spending the night on the ground in BRU? Technical problem?

[brieky]

I know there was a huge delay yesterday, i suppose it will be a technical problem.

[ExSabena]

Flight of yesterday to ORD (Chicago) cancelled due to hydraulic problem.