Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Which ICAO has a Fleet size of 2?

### Inputs:
table_name: table, columns: ['Airline', 'ICAO', 'IATA', 'Callsign', 'Commenced operations', 'Fleet size', 'Headquarters']

### Response:
SELECT ICAO FROM table WHERE Fleet size = 2