ELI5 Flight Delays - how do airports manage major disruptions such as weather cancellations?

When flights get cancelled because of heavy winds, why is it only a proportion of flights and not 100% that stop? Isn’t it a binary decision of: 'safe' or 'too dangerous'? After weather cancels thousands of flights and lots of people are displaced, how to they all get back on schedule when presumably flights for the next few days are already booked up?   ... We explain like i'm five!   Thank you to the r/explainlikeimfive community, and specifically the following reddit users whose questions and responses formed the basis of this conversation: skmotay, mr_gimenez, nil_defect_found & unpopularcrayon   To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Facebook: https://www.twitter.com/eli5ThePodcast/ or send us an e-mail: ELI5ThePodcast@gmail.com