Service documents: service letters, with those not held

duckdb -csv -c "SELECT document_id, issuer, type_label, number, title, latest_revision, latest_revision_date, has_file
  FROM 'https://openairdocs.org/data/latest/service_document.parquet'
  WHERE issuer_kind <> 'authority'
    AND document_type = 'service_letter'
  ORDER BY issuer, number"

Prints the whole list as CSV. It reads the release’s Parquet files over HTTPS, so there’s nothing to download first. Install DuckDB to run it.

SELECT document_id, issuer, type_label, number, title, latest_revision, latest_revision_date, has_file
FROM 'https://openairdocs.org/data/latest/service_document.parquet'
WHERE issuer_kind <> 'authority'
  AND document_type = 'service_letter'
ORDER BY issuer, number

Run it at the DuckDB prompt, or in any tool that reads Parquet over HTTPS. More ways to query the release are on Use the data.