UPDATE at 10:30 a.m. March 19, 2018: Revised to include quotes and photos from Gov. Greg Abbott's visit with the Aga Khan.

HOUSTON — Greeted by an honor guard from Texas A&M University and a brass band from Houston, the Aga Khan arrived in the Houston area Sunday to celebrate his 60th year as the spiritual leader to nearly 20 million Shia Imami Ismaili Muslims worldwide.

For Ismaili Muslims in Texas, the visit is a once-in-a-decade event to celebrate and give thanks to the leader they say is personally responsible for their spiritual and material livelihood. He will be in Houston through March 22.

"He really cares for all of us," said Farrukh Valliani of Irving. "We're really fortunate that we're going through this experience."

Valliani and thousands of other North Texas Ismailis have been working around the clock to prepare for the Aga Khan's visit since it was announced in late February.

1 / 11The plane of the Aga Khan taxies into position after landing at the Sugar Land Regional Airport on Sunday. The Texas A&M Ross Volunteers Company waits on the red carpet.(Michael Wyke / Special Contributor) 2 / 11The Conrad Johnson Orchestra performs for the arrival.(Michael Wyke / Special Contributor) 3 / 11The Aga Khan exits his plane at the Sugar Land Regional Airport Sunday.(Michael Wyke / Special Contributor) 4 / 11The Aga Khan (left) shakes hands with Texas Secretary of State Rolando Pablos during his arrival.(Michael Wyke / Special Contributor) 5 / 11The Aga Khan walks down the red carpet with Texas Secretary of State Rolando Pablos.(Michael Wyke / Special Contributor) 6 / 11Texas A&M Ross Volunteers Company members Connor Sampson, Daniel LaBore and Nathan Hall perform color guard duties during the arrival ceremonies.(Michael Wyke / Special Contributor) 7 / 11From left: Sugar Land Mayor Joe Zimmerman; Dr. Barkat Fazal, president of the Ismaili National Council U.S.A.; the Aga Khan, and Texas Secretary of State Rolando Pablos during the playing of national anthems.(Michael Wyke / Special Contributor) 8 / 11Sugar Land Mayor Joe Zimmerman (left) presents a key to the city to the Aga Khan (right) as Dr. Barkat Fazal, president of the Ismaili National Council U.S.A., looks on.(Michael Wyke / Special Contributor) 9 / 11Attendants wave as the Aga Khan leaves in his motorcade at the Sugar Land Regional Airport.(Michael Wyke / Special Contributor) 10 / 11Attendants wave as the Aga Khan leaves in his motorcade.(Michael Wyke / Special Contributor) 11 / 11Attendants crowd around the plane of the Aga Khan and take selfies after his departure from the Sugar Land Regional Airport Sunday.(Michael Wyke / Special Contributor)

That preparation came to a head Sunday in a formal ceremony at Sugar Land Regional Airport, where some 200 select Ismaili leaders gathered for the official welcome ceremony.

Along with a saber salute from the Ross Volunteers Company of A&M's Corps of Cadets, the Aga Khan was greeted by Texas Secretary of State Rolando Pablos and was presented a key to the city by Sugar Land Mayor Joe Zimmerman. The dignitaries also stood for the playing of both Ismaili and United States anthems, performed by Houston's Conrad Johnson Orchestra.

"The Ismaili community has shown its commitment to strengthening and empowering our state through service, entrepreneurship, and spiritual leadership," Pablos said. "I would like to thank His Highness [the Aga Khan] for his vision, his leadership, and his community's deep friendship with the State of Texas."

Heena Jiwani, a Texan who was at the ceremony, teaches religious studies and spent two years at London's Institute for Ismaili Studies. She said she felt honored to be in the imam's presence Sunday.

"To be here for his arrival is a really big thing," Jiwani said. "He's just a role model for our entire community."

Who is the Aga Khan?

The Aga Khan is the imam of the worldwide Ismaili community, a branch of Shia Islam. Born in Switzerland and educated at Harvard, he preaches tolerance, the value of education and the importance of community service. At age 81, he is the 49th imam of the Ismaili Muslims.

So he's like the pope?

Not quite. For Ismaili Muslims, the title of imam is hereditary — like royal succession. Each imam selects a successor out of his own children, and the Aga Khan can trace his lineage directly to the Prophet Muhammad. The current imam was given the title of Aga Khan when his grandfather died in 1957.

His influence for Ismaili Muslims is as much cultural as it is spiritual. He has created a number of non-denominational charitable organizations around the globe and says it is his role as imam to tend to both the spiritual and material well-being of his community.

The red-carpet treatment

The Aga Khan is a spiritual leader, but he's also a royal without a nation. He often travels the world and is the guest of heads of state. This month, for example, Queen Elizabeth II of England hosted a dinner in his honor at Windsor Castle. He is visiting Texas as an official guest of the state government and met Gov. Greg Abbott on Sunday afternoon.

"We have a state motto - and that motto is friendship. This is a friendship that has lasted many years and that we expect will continue many years into the future," Abbott said at the lunch, according to a press release.

Gov. Greg Abbott meets with the Aga Khan, spiritual leader to Ismaili Muslims, during an official visit celebrating his 60th year as imam. (Farhez Rayani / Submitted photo)

Why Houston?

Texas has a large concentration of Ismaili Muslims, with about 40,000 of the Aga Khan's followers in the region. Houston is home to the Ismaili Council for the United States headquarters.

What's he doing this week?

This is the Aga Khan's 60th year as imam, and he and the Ismaili community are celebrating his diamond jubilee. It is a year of service as much as celebration, all leading up to his visit this week.

As part of the festivities, the Aga Khan will speak directly to his followers in a series of closed sessions.

Where can I go to learn more about the Ismaili faith?

Dallas Morning News reporter Naheed Rajwani recently wrote a personal essay about her experiences growing up Ismaili post-9/11. Read it here or in the March 18 print edition's Points section. Go to the.ismaili to learn more about the Aga Khan's visit to Houston.