I have a new winner: Iberia, which has 44 daily flights between Madrid and Barcelona.
Second place goes to Alitalia, which has 41 dailies (if I counted right) between Milan and Rome.
At least as good as QF
- Air France also has 34 daily flights between Paris and Toulouse.
- Varig has 33 flights daily between Rio de Janeiro and Sao Paulo.
I checked a couple of other routes, and was surprised to see that there are significantly less flights:
- American has 30 flights daily between Chicago and New York
- ANA on Tokyo-Sapporo: 23 flights
- ANA on Tokyo-Osaka: 22 flights
- Air Canada on Montreal-Toronto: 22 flights