Select partner airlines may have flight date restrictions along with capacity controls. (united.com)
Also, booster seats don't have as many date restrictions on them as car seats do, so when you buy one that is not only easy to clean but also durable, you will find that you have a booster that can be reused again and again. (earlymomentsmatter.org)
Optional date restrictions, registration limits and waitlists give you control over enrollment. (d2l.com)