Buddy says:  The answer depends on whether or not there is a clause in the employee’s contract which requires him to travel abroad as part of his duties.  If the employment contract has such a travel clause in place, then the employee must obey your lawful and reasonable instructions to attend the meeting. Where an individual contravenes a contractual term, this gives grounds for dismissal.

If there is no such term in the contract then it may be possible to imply that foreign travel is the norm for a senior person in your industry or that overseas travel was an obvious requirement, although not stated in the contract. However, any attempt to force the employee to travel may result in him resigning and bringing a claim for constructive dismissal (assuming he has over 12 months' service).

If the employee has less than 12 months' service, you could terminate his employment on the grounds that over seas travel is a pre-requisite for the position. If however, he has over 12 months’ service, you may have to consider on what grounds you can legally terminate employment, for instance capability. You would also need to show that the Statutory Dismissal and Disciplinary procedures have been followed. 

Employer information:  In future, when conducting your interview process, you should check that candidates are suitable for the position. Therefore if travelling is a prerequisite for a job you should ascertain if the candidate is capable of travel, does not suffer from agoraphobia or claustrophobia, and has a valid passport.

Also make sure that any relevant employment contracts state any travel requirements, including details of frequency of travel and approximate amount of travelling time.

You should also be aware that your employee's flying phobia may constitute a disability under the Disability Discrimination Act 1995 (DDA). The DDA covers mental impairments which can include phobias. Therefore, it may be wise to seek an independent medical opinion to find out if the phobia has a substantial adverse effect on the employee’s day to day activities.  If so, you will need to consider if there are any reasonable adjustments that can be made to the employee's role (such as limiting travel to the UK only), before moving to dismiss.