The company is claiming that travel provided by the company to one's base and hotel rooms at one's base is impuded income, and is taxable. The rate of the tax is based on the crewmember's gross income. It's a drive by the company to force the crews to give up gateway travel to their base. The company made the six new-hires sign a condition of employment to establish a residence within 130 miles of their base in order to avoid paying travel for them.
It's not only Atlas. They (airlines) are all begining to read from the same playbook. Some airlines are taxing buddy passes. The company requires one to give the buddy's Social Security Number to tax the buddy for the pass.
Actually, Atlas crews got something the rest of the industry doesn't have, gateway travel. However, now that they have it, it's going to be very difficult for the company to take it away. Hence, the taxable income interpretation.