Manali to Leh route open around Mid May to end of May and depends on weather conditions due to heavy snow at Rohtanag pass / Bara La cha and Tanglan La Pass. For safter side you may schedule your programme at fourth week of May onwards from this sector. Route will remain open till end of September/ October – Please check the weather report before your travel.
Srinagar to Leh route open normally by the end of April and again subject to weather conitions. Better to travel May first week or Second week onwards. Route will remain open till end of October and sometime till November.
Flights are open round the year though flight schedule may get change in winter season from October to March.
In Tourism aspect if you are planning for Ladakh, May to September will be preferred month of travel. However tourst season starts from first week of April till October. In the month of April and October nights will be cold enouogh. However days will be warm and sunny and no problem to visit around the places.