If person has 2-3 year longterm disability insurance and becomes disabled and can't work and is under 60 for example which Federal agency benefit would kick in. Is it after two or three years?

If a person with a 2-3 year long-term disability insurance becomes disabled and unable to work before the insurance benefit period ends, they may be eligible for Social Security Disability Insurance (SSDI) through the Social Security Administration. Eligibility for SSDI benefits is determined by the severity of the disability and the inability to engage in substantial gainful activity. It is possible for SSDI benefits to kick in before the expiration of the long-term disability insurance coverage.