Excuse me , Ma ' am . I would like to mail this package door to door via airmail to London . It is a very important package and has to be sent within 3 days .   No problem . But , the postage is much higher than the regular package .   That's fine with me . I am willing to pay for it as long as you can guarantee me the package can arrive in time .   OK . All the registered airmail packages can be received in 5 working days . 