In my opinion, it is unethical for a company to use seniority as a basis for promotion. We can't say that seniority gives desired performance every time, and there are several examples of individuals who are junior and who have just joined a certain organization, but they give better performance than their seniors, and they learn the tasks speedily. It completely depends on the capability and skills of an individual that how he/she adapts to his/her job, and how he/she learns skills. The personality and skills-learning capability of each individual differ in this world, and each individual has his/her own capability of competing with others. An organization could become more successful if it avoids judging juniors and seniors depending on their experience, but organizations could achieve their goals after putting trust in the skills of an employee regardless of the fact that he/she is a senior or junior.