For those with sufficient time, a 10-12 day trek through Solu to the Khumbu and the Sagarmatha National Park is an excellent itinerary both in terms of acclimatization and to observe the changing customs, traditions, and lifestyles as you go from the lower altitude settlements to those in the higher altitudes.
A part of the Himalayan ecological zone, the park was added to the list of UNESCO Natural World Heritage Sites in 1979. The park has three of the world's highest mountains: Everest, Lhotse, and Cho Oyu besides countless other peaks that rise above 6,000 meters from sea level.
Taking a flight is a time-saver, while trekking from Jiri gives you the opportunity to follow in the footsteps of Tenzing and Hillary before their conquest of Everest. With more time to interact with the charming people along the route, you get to see the rich flora and fauna on the long trail. You get the added benefit of natural acclimatization as you go up and down the cliffs and valleys.
The option from Jiri will roughly add 10 days to your trip to the famous Sherpa village, Namche Bazaar (3,500m). The Sagarmatha National Park in which Mt. Everest lies is one of the few places on earth with the rarest bio-diversity and the highest mountains in the world.