For some reason the processing of PayPal's payments is slow at the moment in some cases. This has only affected some of our users, and you could have seen it as a considerable delay in PayPal's ability to clear your credit card payment and inform AirwaySim's server of the success (leading to delay in getting your Credits).
The issue is purely at PayPal's end and I am sure they are working to resolve it.
If you have made an order via PayPal that first didn't work (but was now cleared after hours of delay), and then perhaps made a second order with direct credit card payment, and require a refund of the other one (if you don't need all the credits) be in touch please.
(less than 10 users are affected from what I see, since the PayPal's technical issue is not on all of their servers; most transactions were normal)