Step 2 - API key
The api key is no longer sent in the url as a query parameter.
Now you have to add a header to the request called x-api-key with the API key as the value.
info
Differences between v1.0 to v3:
v1.0 (before)
curl --location --request GET
'http://partners.api.skyscanner.net/apiservices/autosuggest/v1.0/UK/GBP/en-GB/?apiKey=prtl6749387986743898559646983194&query=London'
v3 (after)
curl --location --request POST 'https://partners.api.skyscanner.net/apiservices/v3/autosuggest/flights' \
--header 'x-api-key: prtl6749387986743898559646983194'