Passing event data to a script via an automation

Configuration
1

Hi team.
Ive got a couple of threads up around the place RE this, but this is a more specific question.

At a high level, im trrying to curate a list of all current open flights over my house, using the opensky sensor.

If i manually call the script, via developer tools, i get a result on my remote endpoint.
The automation “works”, but im not getting the callsign sent over. Im sure im missing something simple, ive just been looking at it for too long!

Any ideas?

Script:

add_opensky_in:
  sequence:
  - service: rest_command.opensky_list
    data_template:
      payload: "{\n \"callsign\": \"{{ callsign }}\" \n}\n"

Automation:

- alias: Flight API
  trigger:
    platform: event
    event_type: opensky_entry
  action:
  - data:
      data_template:
        callsign: "{{trigger.event.data.callsign }}"
    service: script.add_opensky_in
2 
- alias: Flight API
  trigger:
    platform: event
    event_type: opensky_entry
  action:
  - data_template:
      callsign: "{{ trigger.event.data.callsign }}"
    service: script.add_opensky_in
3

Thanks! Knew it was bound to be something simple.