We signal them first and ask permission for me to come aboard. How many friendly ships do we pass?
You pass 8 ships that are non-hostile. Note that these are not ones that are closer enough for Chase's spell, but taking into account Nathan's flight and extended vision. Nathan sees more when he goes up high, but he figures this amount is sufficient.
The ships are merchants and a corsair; detail available if you want. Three of them mention spotting the ship (this is during the past six days or more along the course you suspected). They did not recognize it and it did not bother them.