Even though you are over forty, there may be a good reason why you did not get the job. Ask yourself if you are truly qualified for the position. Some older workers have characteristics that keep them from performing the job safely or efficiently, and age is the only available way to screen for these characteristics. Be honest about your situation. People over the age of forty are fired every day for reasons other than age discrimination.
Cost cutting is also a reasonable factor for firing an older employee.
If salary is a factor in a termination decision, the ADEA does not prohibit an employer faced with financial constraints from reducing costs based on personnel cutbacks. An employer also has the right to reduce an employee's salary to current market conditions. Take action to protect yourself. More employees are fighting back when they think they've lost a job or have been held back because of their age. The courts are supporting this trend.