That title certainly got my attention, but I find it to be somewhat misleading.

The F22 Raptors do not have the right sensors to detect some Russian aircraft at night, so I guess you could call them "invisible" when it comes to the radar/sensors the F22 planes have - but it isn't like the planes are invisible like Klingon spacecraft in Star Trek as they are clearly seen when they come within visual range.

And the "unpleasant surprise" is when F22 pilots are surprised when the Russsian aircraft come within visual range not that they are surprised that the planes are actually invisible and suddenly pop into view when they drop their Klingon-like cloaking shields.

I don't see "uncomfortable" listed in the excerpt, but I can see how a plane suddenly appearing alongside would cause pilots to be uncomfortable.