Too many requests in a given amount of time

I am getting the error like Too many requests in a given amount of time..
I am having a multiple API calls, In a short period of time, Because of that, I am getting above error message.
Please help me, How I can make multiple API call In a short period of time.

It looks like you’re using FlightXML3. This version has request rate limits per plan tier. Moving up the tiers will grant higher rate limits.