The FTSE 100 jumped to a four-week high on Tuesday as investors' fears of an impending US military strike on Syria eased and the economic outlook for China improved.London's benchmark index finished 53.25 points higher at 6,583.99, a gain of 0.82%; the last time it closed higher was on August 14th when it ended the day at 6,587.43."The FTSE 100 is knocking on the door of 6,600 for the first time since mid-August, as investors look to make gains before the crucial Fed meeting next week," said Market Analyst Chris Beauchamp from IG. Friday's disappointing US non-farm payrolls figure has increased hopes that the Federal Reserve could delay a move to taper its stimulus programme until later this year.Markets started on the front foot this morning on the back of a continuing improvement in economic data from China with the third-quarter outlook for the Asian powerhouse continuing to brighten. Industrial output, fixed-asset investment and retail sales strengthened during the month of August, with all three economic indicators rising by more than expected. This followed yesterday's news that exports rose more than expected in August, while consumer price inflation eased.Stocks then extended gains in the afternoon as Wall Street indices reacted positively to developments in Syria, with the S&P 500 extending its recent winning streak into the sixth day, its longest string of positive sessions since mid-July.Positive developments in SyriaSyria said today that it has accepted a Russian-backed proposal to give up chemical weapons to international control in an attempt to avoid US military action, according to Russian news agency Interfax. This follows the request by Russian Foreign Minister Sergei Lavrov yesterday to give up any chemical weapons they may.Syria's Foreign Minister Walid Muallem said that he agreed to the proposals to "remove the grounds for American aggression".IG's Beauchamp said: "If you'd been asked to suggest a possible starting point for a solution to the Syrian crisis, I suspect Russia would not have been at the top of the list. "Nevertheless, it now seems as if Moscow could find a way to take some of the heat out of the situation. As a result, markets have breathed a sigh of relief, with stock indices gaining and gold and oil giving back much of their recent gains."All eyes now turn to US President Barack Obama ahead of a speech in Washington tonight where he is expected to outline his intentions for the next course of action regarding Syria.FTSE 100: Airlines flying high, miners track metals lowerAirline groups IAG and easyJet were flying higher with crude continuing to pull back from its recent highs as fears over turmoil in the Middle East ease. Elevated oil prices have pressured both stocks over the last few weeks on concerns over the knock-on effects to jet fuel costs. Shares in easyJet were also helped by comments from Chief Executive Carolyn McCall who said in an interview that the company will be "Europe's preferred airline in five years' time" due to its low-cost operating model.easyJet rose yesterday after Bank of America Merrill Lynch predicted that October's fourth-quarter trading update would see a continuation of its robust yield performance, and suggested a special dividend could also be on the cards. Monday also saw the company add two new routes, with seats to go on sale from next month.Financials were also performing well today with RBS, Standard Chartered, Aberdeen Asset Management, Prudential, Hargreaves Lansdown and Aviva among the highest risers.Leading the downside were the miners as metal prices fell across the board. Precious metals peers Randgold and Fresnillo were among the worst performers as gold futures dropped to a two-week low. Recently-merged Glencore Xstrata however bucked the trend after lifting its synergy target to at least $2bn next year as the miner vowed to cut costs and improve operational efficiency. Pharma giant GlaxoSmithKline fell sharply after US regulators set out requirements for generic versions of its lung drug Advair, sparking competition concerns over when patents run out in a few years' time.Costa and Premier Inn owner Whitbread was also down after seeing sales growth slow from 13.8% in the first quarter to just 10.8% in the second as the hot summer weather hit demand at its coffee shops.Broker comments were also moving a number of blue-chip stocks: Drinks giant SABMiller was on the climb this morning after HSBC upgraded the stock to 'overweight'; consumer products group Unilever was lifted by Deutsche Bank to 'buy'; and Babcock was higher after JPMorgan labelled the engineering support services company as its top pick in the sector.FTSE 250: Ashmore jumps, Oxford Instruments slumpsRecord subscriptions helped emerging markets asset manager Ashmore to drive strong net inflows into its funds in the year to June, giving the share price a boost this morning. Strong net inflows of $13.4bn led to a 22% increase in assets under management (AuM) to $77.4bn during the year, with average AuM rising 13%.Oxford Instruments was a heavy faller after saying that while growth in the order intake rate in Industrial Products and third party Service is encouraging, slowness in R&D markets in the Western economies means that the year is likely to be more second half-weighted.Shares in chip designer Imagination Technologies jumped today ahead of an Apple event in California where the tech giant - a key customer for Imagination - is expected to unveil its latest iPhone.FTSE 100 - RiserseasyJet (EZJ) 1,358.00p +7.18%Royal Bank of Scotland Group (RBS) 356.00p +4.71%International Consolidated Airlines Group SA (CDI) (IAG) 319.80p +4.68%Carnival (CCL) 2,450.00p +4.26%Aberdeen Asset Management (ADN) 384.10p +4.04%Standard Chartered (STAN) 1,511.00p +3.81%Legal & General Group (LGEN) 199.60p +2.99%Prudential (PRU) 1,171.00p +2.99%SABMiller (SAB) 3,174.00p +2.88%Weir Group (WEIR) 2,344.00p +2.85%FTSE 100 - FallersRandgold Resources Ltd. (RRS) 4,689.00p -4.58%Fresnillo (FRES) 1,225.00p -3.47%GlaxoSmithKline (GSK) 1,598.50p -2.53%Whitbread (WTB) 3,138.00p -2.43%Eurasian Natural Resources Corp. (ENRC) 221.00p -1.69%Vodafone Group (VOD) 207.90p -1.19%BG Group (BG.) 1,205.00p -0.99%Rolls-Royce Holdings (RR.) 1,131.00p -0.26%Tullow Oil (TLW) 1,057.00p -0.19%Vedanta Resources (VED) 1,188.00p -0.17%FTSE 250 - RisersAshmore Group (ASHM) 382.20p +5.32%Imagination Technologies Group (IMG) 302.00p +5.19%Fenner (FENR) 389.50p +5.01%Laird (LRD) 234.70p +4.96%Ferrexpo (FXPO) 187.00p +4.64%Galliford Try (GFRD) 1,070.00p +4.59%Henderson Group (HGG) 187.10p +4.53%Synthomer (SYNT) 249.20p +4.40%Ocado Group (OCDO) 365.00p +4.29%Greggs (GRG) 438.70p +4.15%FTSE 250 - FallersAfrican Barrick Gold (ABG) 166.40p -9.37%Oxford Instruments (OXIG) 1,404.00p -7.02%Moneysupermarket.com Group (MONY) 168.50p -2.21%Pace (PIC) 280.50p -2.13%Centamin (DI) (CEY) 46.00p -1.96%International Personal Finance (IPF) 640.00p -1.54%Polymetal International (POLY) 756.00p -1.50%Essar Energy (ESSR) 136.70p -1.37%RPS Group (RPS) 257.00p -1.19%ITE Group (ITE) 288.50p -1.13%BC