Spain's fast-fashion king Amancio Ortega has added $3.7 billion to his personal fortune after Inditex SA, the world's largest clothing retailer, announced brisk sales, sending shares up 6 percent. Sanford C. Bernstein analyst Jamie Merriman said the company results were strong and show a "stellar start" to the quarter.

Ortega, who passed U.S. investor Warren Buffett as the world's second-richest person in June, is $9.5 billion away from leapfrogging Microsoft founder Bill Gates as the world's richest person, as of mid-day trading in New York, according to the Bloomberg Billionaires Index. 

Ortega began building the Spanish fashion empire with his siblings and soon-to-be wife in 1963, making women's bathrobes and other clothing in their home in northern Spain. He opened the first Zara store in 1975 and created Inditex a decade later. Its initial public offering was in 2001 and since then, Ortega has collected more than 4 billion euros ($4.5 billion) in dividends, investing much of it in commercial properties in major U.S. and European cities.

Those real estate holdings amount to about $8 billion of his net worth, with Inditex making up more than $63 billion. Ortega has risen from the world's seventh-richest person since March 2012, when the Bloomberg index debuted and his fortune was at $38 billion. Gates had $62.5 billion in March 2012 and passed Mexico's Carlos Slim to reclaim the world's richest person spot in May 2013 when Microsoft hit a five-year high. Microsoft was up about 0.4 percent at 2:10 p.m. in New York, giving Gates a fortune of around $80.6 billion. Ortega has $71.1 billion.

The second-richest person in Spain is Ortega's daughter, Sandra Ortega-Mera, who inherited her 5 percent stake in Inditex when her mother died in August 2013. She has a $7.2 billion fortune after the Inditex rise.