andy mcilvaine , 33 , got talking to southwest staff during his flight to propose to his girlfriend in maine last october .
touched by his story , they gave him a $ 100 voucher as a gift .
after he wrote to thank the ceo , the company threw the couple a shower at bwi airport in baltimore on april 1 .
baltimore-based mcilvaine and dallas-based kelley mulsingeron spend much of their relationship flying to visit one another .