The airplane that operates flight to Lukla are small and the total limit of weight per passenger is only 15 KG including your main luggage and hand carry. So, we suggest you to pack your gear carefully and take only the necessary things on trek and leave the extra stuff in the hotel in Kathmandu which is returned after you return from the trek. You can take some Kg more by paying some extra charge however it is not guaranteed for the extra luggage as it is available only when they have spaces available.