Narrative:

Aircraft X was cleared for takeoff off. After the clearance was given the local assist controller was instructed to get the local controller out for a break. I briefed the local assist controller on everything that was going on. I let him know that aircraft X just rotated and that he will need to be switched to departure. As soon as the brief was done I immediately noticed that an adjacent airport had an aircraft in the right downwind at 1;700 feet and climbing. Aircraft Y was doing 150 knots climbing through 1;700 feet. I told him to make sure that you call traffic on that. He immediately called up the adjacent airport and instructed them to turn the aircraft to heading 090 degree heading. The controller responded with a 'huh'. What did you say? At the same time the local control called traffic to aircraft X but aircraft X said that they did not see the aircraft. A traffic alert was given to aircraft X and they were advised to turn right immediately. The two aircraft passed without incident!aircraft Y didn't come on frequency until about 1 mile later. (This is now 1 mile inside of our airspace. Aircraft Y was coming to us directly down our departure corridor at a terrible altitude and the tower didn't switch him to us soon enough for us to do anything about it. When we tried to coordinate with the airport the controller had no idea what was going on. We did everything that we could do to avert a possible disaster and luckily it was averted.when on a west configuration he adjacent airport needs to have all aircraft that will be coming into our airspace either make a left downwind departure or have them all on a 090 heading or up over the freeway to prevent this from happening again.

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Original NASA ASRS Text

Title: Aircraft on a SID off one airport was in direct conflict with a VFR departure from another airport next to it.

Narrative: Aircraft X was cleared for takeoff off. After the clearance was given the local assist controller was instructed to get the local controller out for a break. I briefed the local assist controller on everything that was going on. I let him know that Aircraft X just rotated and that he will need to be switched to departure. As soon as the brief was done I immediately noticed that an adjacent airport had an aircraft in the right downwind at 1;700 feet and climbing. Aircraft Y was doing 150 knots climbing through 1;700 feet. I told him to make sure that you call traffic on that. He immediately called up the adjacent airport and instructed them to turn the aircraft to heading 090 degree heading. The controller responded with a 'huh'. What did you say? At the same time the local control called traffic to Aircraft X but Aircraft X said that they did not see the aircraft. A traffic alert was given to Aircraft X and they were advised to turn right immediately. The two aircraft passed without incident!Aircraft Y didn't come on frequency until about 1 mile later. (This is now 1 mile inside of our airspace. Aircraft Y was coming to us directly down our departure corridor at a terrible altitude and the tower didn't switch him to us soon enough for us to do anything about it. When we tried to coordinate with the airport the controller had no idea what was going on. We did everything that we could do to avert a possible disaster and luckily it was averted.When on a west configuration he adjacent airport needs to have all aircraft that will be coming into our airspace either make a left downwind departure or have them all on a 090 heading or up over the freeway to prevent this from happening again.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.