"Open the hangar—here comes the airplane!” is what a parent says to a young child to open the child’s mouth (the “hangar") for food (the “airplane"). The saying has been cited in print since at least 1969.
Similar sayings include “Open the tunnel—here comes the train!” and “Open the garage—here comes the car!”
10 January 1969, Life magazine, pg. 81, cols. 1-2:
“Eat!” he commanded again, and then, flashing back to his own childhood and in overwhelming filial appeal to his mother, he added, “Open the hangar door, here comes the plane, rrrrrr,” as he bore down with a forkful of salad. His mother opened the hangar door, though she was so convulsed with laughter that she found it hard to swallow.
16 February 1972, Cleveland (OH) Plain Dealer, “A Special Someone: Michael” by Paula Slimak, pg. 4B, col. 2:
Meals can be fun for 2-year-old Michael Miarka, whose paternal grandmother started a mealtime ritual.
She’d say, “Open the doors, here comes an airplane.”
And Michael would open his mouth, andlet the airplane (a fork) land—loaded with food.
Google News Archive
24 April 1973, Bangor (ME) Daily News, “Cheese Whiz, toothpaste” by Nancy Stahl, pg. 5, col. 1:
In desperation, I took to cavorting around the kitchen wearing goggles and a white scarf, waving a spoonful of strained beets, flapping my arms and chortling, “Here comes ‘The Spirit of St. Louis/’ Open the hangar!”
The Bride of the Delta Queen
By Janet Dailey
New York, NY: Harlequin Books
“Any minute I expect to hear you say, open the hangar, here comes the airplane, just as if you were feeding a child.”
Big Lessons for Little People:
Teaching our kids right from wrong, while keeping them healthy, safe, and happy
By Lois Nachamie
New York, NY: Dell Pub.
“Here comes the airplane! Open the hangar wide!”
A Beginning Singer’s Guide
By Richard Davis
Lanham, MD: Scarecrow Press
It may hearken back to being fed as a child when Daddy told you, “Open the hangar, here comes the plane.”
The everything baby’s first food book:
Tasty, nutritious meals and snacks that even the pickiest child will love—from birth to age 3
By Janet Mason Tarlov
Holbrook, MA: Adams; Hadleigh: BRAD
Tricks of the Trade: The Old Airplane-in-the Hangar Trick
I didn’t even try this trick with my son for months because I thought it was just an old cliche, but “Here comes the airplane! Open the hangar doors!”
Let’s Be Jolly!
By Janet Dailey
New York, NY: Kensington
He flicked an impassive glance in her direction and started to bring the spoon to her mouth. “Any minute I expect to hear you say, ‘Open the hangar, here comes the airplane,’ just as if you were feeding a child.”