GST on air export

In your Query there is 2 set of Transaction is involved:

1. Between You & Hongkong courier Company .

2. Between You & Indian Company.

Note : You are in Taxable territory (India)

Now let's take First Condition.
As per Section 13(9) of IGST Act Read with sub-Section (2) , "The POS of transportation of Goods , Other Than by way of MAIL OR COURIER, shall be the destination of Goods . here its specifically mention, if it is Not Courier Services, then in this case the subsection (2) of 13 of IGST will triggered . So for courier services POS will be location of Receptient (YOU).
Hence in term of Definition for Import Services provided in Section 2(11) , it's IMPORT OF SERVICES. (Do the RCM )

Note : It's not merchant export



Now come to your 2Nd condition : As per provisio under Section 12(8) : transportation of Goods is to a place Outside India , the POS shall be the Place of Destination of Goods . Hence as You are the supplier for Indian company , you are liable charge IGST on your bill to Indian company (Even though Indian company & you are in same state)