Identify Unique Unordered City Pairs in Flight Log

FLIGHTS

+----------------+---------------+
| departure_city | arrival_city  |
+----------------+---------------+
| NYC            | LAX           |
| LAX            | NYC           |
| ORD            | ATL           |
+----------------+---------------+

Scenario

You work with an airline flight log. Each row records a flight’s origin and destination city. Management wants to see all distinct city pairs regardless of flight direction (NYC–LAX is the same as LAX–NYC).

Question

Write a SQL query (or equivalent Python/Pandas snippet) that returns the unique unordered city pairs from the FLIGHTS table, treating (A,B) and (B,A) as the same route combination.

Hints

Normalize the order of the two cities—e.g., use LEAST/GREATEST or sort values—then GROUP BY the normalized pair.

Unique Unordered Flight City Pairs

Table FLIGHTS

column	type	constraints
departure_city	VARCHAR(3)
arrival_city	VARCHAR(3)

Sample data:

arrival_city	departure_city
LAX	NYC
NYC	LAX
ATL	ORD

Expected output

Each unordered pair of cities appears once, with the two cities normalized to a consistent order (e.g., alphabetical within the pair).

city_a	city_b
ATL	ORD
LAX	NYC

Hints

1. Normalize the pair order using LEAST and GREATEST (or equivalent CASE logic).
2. Use DISTINCT (or GROUP BY) on the normalized pair to remove direction duplicates.