If there's one thing I've learned to love over the course of shipping pilots, it's the fact that their feelings for each other are hardly ever explicitly stated - those two crazy kids are so unlike everyone else in love, they can't even manage to state their effect on each other in the same words everyone else uses, not without incredible difficulty anyway.
And the way they do express it is not the way everyone expresses it - in the normal world, challenging each other to a beatdown or holding each other's gaze for several seconds too long isn't really taken as a sign of undying love.
So what is pilot-speak for "I love you/life without you is completely miserable"? Here's a few examples to start off with:
"I thought you were dead." "Well, I thought you were in hack." "It's good to be wrong."
Every time they forget and use each other's names instead of callsigns over the comms.
The final kiss in Scar.....and Lee finishing the toast at the end for Kara.
"Whatever it takes."
"This is all that matters."
Pilots code their feelings for each other in seemingly ordinary words and some not-so-ordinary body language ALL THE TIME, and even I can't begin to untangle all those times - do discuss, and since there is loads that I've missed out on, feel free to add to the list!