Directions to the ETN bus stop at the Guad airport?

I do not believe that ETN services the airport.  They only stop at the designated inter-city terminals in Guadalajara (Central Comoniera in Tonala, Periferico Sur by the Elektra warehouse and the western terminal at the Periferico & Vallarta).

You need to find out what terminal your friend's friend is arriving at and probably have him/her take a taxi from there to the airport to meet your friend.

The ETN bus from Barra de Navadid (Manzanillo) does make a stop at the airport.
Here is a link to directions.
ETN - GDL airport

We returned from Barra de Navidad on Feb 8th and (disappointingly) were told at our stop in Manzanillo that the buss would be unloading at the Guad airport before going to the Guad terminal.  None of this was announced on any bus scheduling that we knew of.  From the time we turned South off the Periferico onto the Chapala highway and did the airport dropoff and arrived at the ETN terminal was an additional 45-minutes for us.  I was curious as to where a bus terminal was at the Guad airport as well..so I tried to pay attention.  If my memory serves me right, when the bus got to the roundabout it went to the left there, traveled down a ways then turned two rights and we stopped at a small bus terminal.  I didn't see it marked specifically for ETN, so other bus lines may use it as well.  More than half the folks on the bus got off there....no one got on.

The ETN bus with service to and from Manzinillo and area always goes through the airport. Always has. If you look online for a ticket it is there very clearly....Guadalajara Aeropuerto. The same bus services the usual bus station. This is how people get to and from Colima and the International airport in Jalisco. For those of us at Lakeside the airport stop is much more convenient and quicker.