Yes the answer by Philip is correct in this instance in regard to aircraft interiors, although in aircraft maintenance terminology, it usually refers to a pressure bulkhead, such as either side of the wheel wells, or at either end of the fuselage, such as between the cabin and the tail section.
Rainbow baby. A rainbow baby is a baby that is born following a miscarriage or still birth. In the real world, a beautiful and bright rainbow follows a storm and gives hope of things getting better. The rainbow is more appreciated having just experienced the storm in comparison. The storm (pregnancy loss) has already happened and nothing can change that experience. Storm-clouds might still be overhead as the family continue to cope with the loss, but something colourful and bright has emerged from the darkness and misery.
I've tossed out a lot of info about the symbolic meaning of rainbows here. In the end, the simplest interpretation is this: The best message and meaning of rainbows is assurance and appreciation. Beholding a rainbow is a gift, and when we encounter their beauty, it is the perfect time to be grateful for all the gifts in our lives.