Final answer:
Air traffic controllers on duty perform tasks involving judgment and choice, which are considered discretionary functions under the Federal Tort Claims Act (FTCA), making the statement true.
Step-by-step explanation:
The question "Air traffic controllers on duty are engaged in a discretionary function for FTCA purposes." addresses the scope of duties and liabilities under the Federal Tort Claims Act (FTCA). By law, discretionary functions or duties are those that involve an element of judgment or choice and are not compelled by statute or regulation.
Since air traffic controllers must make judgment calls and decisions based on varying circumstances, their actions are considered discretionary functions under the FTCA. Therefore, the answer to the question is A. True.